Have you ever noticed that the pacing, tone, and story development of Pokemon changes after Ash is hit by lightning in the early episodes? How Ash and his world are relatively normal until after that incident? I have a theory.
The accident with the bike put Ash into a coma. Days later, he was found and hurried to the hospital and treated with heavy medications. This is why Team Rocket became less menacing. The medication took effect and stabilized his coma dreams so that, instead of being terrifying, they became idyllic. They allowed him to live out his Pokemon Master fantasies.
After the beginning episodes, the series is the result of Ash's subconscious mind fulfilling his desires as well as attempting to escape reality. Should Ash realize he's in a coma, he would wake up and suffer brain damage, so he must take down all of his mental barriers one by one.
If he can do that, he can come to grips with who he is and escape his coma. Further evidence comes from the realization that even though his journeys take him vast distances, he never usually travels by bike due to having developed a phobia of them.
The coma and fantasy explains why he never changes much, physically. It explains the worldwide socialism, as he thought up a safe system of government that would run smoothly and keep the world going, allowing his adventures to work like they do.
It also explains how a child can go off on his own into a world full of dangerous and untamed animals. In addition, it explains why every town has the same police officer every Pokemon Center has the same nurse.
Joy and Jenny he knew from his hometown and they act as a safety net or anchor, allowing him to feel safe no matter where he goes. They represent stability. The professors represent Ash's ideals, which is why Gary became a professor.
The fantasy also explains why every time he enters a new region that virtually no one has heard of him, despite his conquests. How else could Paul, the rival of the Sinnoh area, not know of someone who placed in at least the top sixteen of all three leagues and destroyed the Orange League and Battle Frontier?
Moving on to the characters closer to him...Ash's traveling partners are aspects of himself he can enjoy but cannot associate with himself.
Brock is Ash's repressed sexuality. Ash fell into the coma a virgin and, as such, needed an outlet for his growing sexual frustrations. However, since he can never experience sex, Brock must never succeed. Brock's stay with Professor Ivy was an attempt by Ash's mind to surpress his sexuality.
Brock isn't just a projection of Ash's sexuality, but also a projection of Ash's fatherly instincts. He leaves his siblings to journey with Ash because he can't cope with having that much responsibility.
You may notice that James got much more dialogue in this part of the series, as well as getting more touchy-feely with his Pokemon and exposing much of his backstory. Ash didn't enjoy this much, which is why Brock returns, horrified, and refuses to speak about it.
Ash's subconscious was repressing him at the time so, other than a general feeling of dread, he has no idea what happened. Further evidence of Brock being Ash's sexuality is that he keeps returning the series after Ash meets a new female aspect of himself.
Misty is the first such aspect we encounter. Because she is the first and is merely an aspect of Ash are explanations as to why Misty plays such a prominent role in the show but is ultimately unattainable (since he never really knew her before the coma).
Since Misty is his initial love interest (if only subconsciously), he needed her to reach a certain level of womanhood. He felt that people could only have relationships after they've matured.
In practice, however, he finds he can't cope with it, as he lacks real-world experience. He wants the normal, pushy, arrogant Misty he knew...thus, not letting her keep Togepi. We can see this arc in the constant berating of his sexuality, but her eventual mellowing until she had faded into the background.
Since Ash was quite attached to her, this was traumatizing. After this experience, anyone around him "threatening" to mature quickly ends up leaving only for another, more naive fill-in to enter his life.
Gary Oak is what Ash wants to be. He is wish fulfillment. He succeded and then settled down to a normal life. Ash needs someone to succeed in his world or he won't be able to validate it and will start questioning why he is where he is. It's a subconscious trap to keep him from becoming too aware of his situation.
His mind must have figured out that awareness of the coma would snap him out of it, so it took something the boy already loved and build a way out for him with it. However, Ash is too complacent to make a final stand and fight his way out of it, and cannot escape.
This is why he keeps encountering legendary Pokemon. They're his mind's way of showing him he can do great things if he tries. It's a way to encourage him to push forwards.
Team Rocket are the qualities of himself that Ash deems "negative" but is coming to terms with. Jessie and James want to appease Giovanni, Ash's father figure. To achieve this, Jessie will trick the submissive James into doing her bidding. Meowth especially wants to appease him because he remembers the good times with Giovanni.
This places Meowth in a category known as Ash's (corrupted) innocence. This is apparent because Mouth is able to speak. In fact, the whole reason Meowth can speak is so Ash can eventually accept the aspects of Team Rocket as parts of himself.
Ash had issues with his father, so he put him atop the evil corporation and demonized him. There may be an actual Team Rocket (in the real world), but it's doubtful that Ash's father is their leader. Ash likely feels the split between his parents was partly his fault, but also partly blames his father.
The split caused his mother to move out of the city down to Pallet Town and is one reaon why Ash initially embarks on his journey: to escape the turmoil at home. The whole organization, including Butch and Cassidy, is symbolic of his inability to escape his father's machinations.
James is implied homosexuality (which does not necessarily make Ash homosexual) and gullibility, while Jessie is vanity and manipulation. Since Meowth has the potential for rehabilitation and doesn't want to be evil, this once again fits with the conflicting personalities and demonized-self theory.
Team Rocket crossdresses because Ash is exploring his sexuality (a different facet than what Brock represents) and this was a method that allowed his gay/vain side to experiment freely. When he found that it wasn't something for him, he "free" side stopped playing with it.
Max came with May. He played the ego and she played the id with great aspirations in that "session." They worked for a little while but, with Ash being a teenager, his sexuality had to come back into play. He kept reinventing himself and eventually wrote new aspects, but his mind slowly brought the old ones back as a crutch to make the transition easier.
Dawn is Ash giving himself a chance to love. Since he already established Misty as someone he's not likely to go anywhere with, he created a new super female - one that was more like him and less violent. You may note that while both May and Misty had no tolerance for Brock's behavior, Dawn seems to try to shrug it off.
Tracey, the breeder, was a possible future for Ash that he discarded. This future was one that he sent off to work with the professor (Ash's ultimate ideal of a father figure) when Tracey disrupted the dynamic Ash had with his other possibilities.
With Ash's mind fighting the coma and Ash viewing this person as a companion, Tracy was quickly replaced with a more threatening rival.
Pikachu represents Ash's humanity. This explains the episodes where they get separated and Ash desperately wants to find him, even to the point of working with Team Rocket (aspects of himself he would never normally associate with), but for some reason cannot.
Team Rocket wants to steal Pikachu and hand him over to Giovanni. Jessie and James will always oppose Ash because he is terrified of the thought of his humanity lying in the hands of his father. However, this is the same reason he will work with those aspects of himself in order to save his humanity.
Ash couldn't evolve Pikachu because that would mean challenging his concept of who he was, which was something he wasn't comfortable with while still working through his original issues.
The narrator is Ash's higher mind, recapping and explaining the progress he's made and the tribulations he will face, allowing insight into how to best awaken him.
Team Rocket's methods gradually become more and more ludicrous because Ash is only a child dreaming these things up. That is why Team Rocket's disguises are always believed. He knows it's them (at least on a subconscious level), but chooses to ignore it so he can better himself.
In a sense, the Ash who wants to escape is sabotaging the Ash who wants to stay lost in his mind so that there can be more conflict and, hopefully, an eventual escape. The escape is a consequence of coming to terms with who he is. As mentioned previously, Team Rocket are a method to Ash to deal with grounds he's uncomfortable with tackling on his own.
You may recall that early in the show, there were animals and references to animals. For example, the fish in the aquarium of the Cerulean City gym or that the Pokedex lists Pikachu as "rat-like." These animals don't matter to Ash's psyche, so they don't come into play much.
If Ash loved puppies, everything would be about different breeds of dogs and a dog fighting circuit, but as the series goes on, you see fewer realistic animals and more Pokemon. This could be a sign of Ash's mind deteriorating.
As he's in the coma, he's losing concepts of some animals and machinera and replacing them with Pokemon. It could explain things like electric Pokemon working as power generators; these are signs that his memory of the old world is slipping more and more as time goes by.
The Pokemon realm will be idealized continuously the longer he has no stimulus from the real world. Ash may or may not be mentally deteriorating, but he is becoming more accustomed to his fake world's rules. The wild Pokemon are his rationalizations for the functioning of his created fantasy. It's the "a wizard did it" syndrome. If he doesn't know how it works, his mind says Pokemon.
The Pokemon in Ash's team, however, serve the purpose of displaying his issues and aspects of himself. For example, Charmander represents his sex drive (not his sexuality, like Brock). At first it's a cute, easy thing to control, but eventually becomes a raging inferno of disobedience since Ash has no real understanding of his sexuality (thus has no way to vent or keep it in check).
Bulbasaur was his unwillingness to change, reflected in when it declines to evolve and almost decided to stay behind unless he battled it. Squirtle was his willingness to follow the lead of others, as evidenced by the gang it ran with. Even though he ran the gang, they were viewed as one group and Ash's subconscious gave him the strongest one.
Butterfree was his crushing loneliness, which he dealt with when he released it to join a flock. His bird types are his recklessness, always willing to sacrifice something at a moment's notice for the win. When Ash is trading Pokemon, it's an attempt to push his own problems away on someone else. However, he realizes this and usually trades back very quickly.
Not only are Ash's Pokemon a manifestation of different parts of himself, the Pokemon of other trainers are as well. Koffing and Ekans were symbolic of Team Rocket's willingness to change, hence their evolutions. Once his mind was able to overcome that roadblock and allow them to change once, it gave him the chance to truly change.
An interesting not is that Pupitar is a rationalization: a Pokemon a rival caught before they met. Even Ash would become suspicious if everyone he met had no carry-over Pokemon from previous places he had been to.
Other trainers are more direct forms of his issues - ones he must either come to terms with or outright surpress. Gym leaders are more primary aspects of his personality, with each Pokemon being stronger than the last to display a level of skill he could only be capable of if he gave into it.
In effect, he is doing battle with a part of him that he would rather not have in control. Originally, Ash had the battles, which evolved into team battles and contests. The explanation for this is that his issues became more and more complicated and the means of deeling with them needed to become more complex. The fact that he uses issues he has already dominated to win is a sign he's growing stronger.
Ash releases his Pokemon because his mind is forcing him to get go of them. The second he raises an overpowered team, a tournament comes up and, after fighting his way through it, he has to go to a new land for new challenges. However, with an overpowered team, there won't be any challenges or any way to motive him further.
The Ash that wants to stay in the coma and keep journeying hands his solved issues over to Professor Oak so he can continue and overcome the unresolved ones. This is essentially his mind forcing him to deal with his issues.
Ash's rivals and the Elite Four are ultimately the strongest part of this cycle. Having Pokemon that are essentially godlike, they represent both what can be attained and what is unattainable. Ash's rivals are all possible futures he envisions for himself (note they are all older than him).
This originated with Gary Oak, someone Ash knew from real life and built up into a sort of god within his mind. However, Gary progressed and changed to suit Ash's vision of himself and his ultimate desire, eventually settling down into a professor role after beating the Elite Four.
With Gary Oak in retirement, his mind needed a new rival for him. Thus the births of Richie (the good aspect of his rivalry) and Paul.
Paul is his mind's last ditch efforts to snap him out of it - to force Ash to actually come to terms that this perfect world is not the best option or path to waking up. Paul is Ash's shadow, one that wants to push on even harder and harder. He is the part of Ash that will stop at nothing to escape the coma world.
Mewtwo is a new form of treatment, done with electical impluses and a machine to know Ash out of it, taking down every last one of his mental guards (the original Pokemon in the movie). In Ash's mind, Mewtwo and his clones were (in the real world) the treatment for the mental safeguards that were protecting Ash and keeping him comatose: the Pokemon of his world.
The clones were counters to the issues Ash had thought solved and each appeared to Ash as the exact copy of his defense. The clones didn't play by the rules of Ash's world. They didn't use any special attacks or moves. They just beat down their counterpart through brute strength. The treatment was working.
There were side effects. The electric jolts were beginning affect Ash's nervous system. If the treatment continued, he would be paralyzed. His mind manifested this in the dream world by petrifying him. Were it not for the end of the treatment by Ash's mother, who knew her son wouldn't want to live in a world he couldn't explore, Ash would have remained as stone forever.
After this, Ash needed to recover from the damage caused by the electric therapy. In order to reduce the danger Ash's consciousness felt from it, his subconscious began downplaying the effects in this world, which is why Pikachu's electric attacks - once noted for their strength by Team Rocket - no longer have any effect on Ash, other than comic relief.
As we can see, Ash may well have been trapped forever in this world. However, like every dream, like everything, there is a beginning and an end. What would happen if Ash never recovered?
In his hospital room, we see Delia, obviously distraught. She's talking to a doctor with a grim look on his face. The man is saying their insurance is up and the boy has had no change in brain activity in years. The shock of taking him off life support has a very small chance of awakening him.
She tearfully agrees.
Back in Ash's world, he has finally defeated the Elite four and, one by one, the people around him disappear. Eventually, everything is black. Pikachu comes dashing toward him, glowing brighter and brighter in the darkness. Eventually, he reaches Ash and the two embrace one last time.
In the hospital room, his life signs fading, Ash mutters his final words.
"I...want to be...the very...best..."
He will die never having known his dream, except as naught but a dream. When he came back to reality, he knew it all for the lie it was, knew it as his imagination. Knowing that all his efforts, ambitions, and friends were nothing, he will let go.
As he utters his final words, he barely opens his eyes and sees the silhouette of his mother, her face hidden by her hands wiping away tears. They make eye contact and one final realization fills him before he loses all strength.
He sees that his mother was holding out hope that he'd recover all that time. He sees her and finds that her hope had been broken as she'd come to the realization that she'd outlived her only child. He dies knowing that he is loved, but that it mens the one person closest and most real to him is utterly crushed.
Still, there are other possibilities. The fountain of time flows in mysterious ways. One could not go back against the current, such as Gatsby. However, one could never see what is waiting for him downstream. Ash finally defeats Lance, only to be confronted by not Gary Oak, but a mute mirror image of himself.
The voice of the narrator speaks to him, telling him that now he can finally escape the prison of his own mind. One by one, his friends appear and melt away into more copies of himself, cheering him on. After a long, tough battle against himself with the assistance of all his Pokemon he had ever befriended, he jolts awake.
In his hospital room, he sees his parents, asleep. He finds himself unable to speak.
Ash pushes forward toward his recovery. He goes through physical therapy, training harder and harder with rehabilitative Pokemon until he can walk on his own again. This time, an older and wiser Ash sets out on a jorney.
Just like last time, he's late getting to Professor Oak's laboratory. When there's only one Pokemon left...he suddenly recalls all his memories of his "life" and realizes all his friends are gone forever.
As he sets out with his new companion, he finds the world is darker than he imagined. More "real." Pokemon and people die. He, too, has aged.
He vows to become the Pokemon Master he dreamed he was. He vows to himself. He vows to "them."
"I WILL be the very best!"