Keep in mind there are many things in the anime that don't match what happens in the game.

Yep, and Ash's level 100 Pikachu still loses to things with levels below 20. See what Yoshi said above.

He manages to beat every gym leader, yet lose to a level 4 starly.

He never actually beats the gym leaders, though. He inevitable loses or ties and is given the badge out of kindness, due to an unrelated incident, or through a technicality. I mean, how many badges over the course of the series has Ash outright and legitimately won?

It's anime...nothing makes sense in it.

lol of course i doesn't
anime hooks you then just fails after it has your attention

I think this would've been helpfull a while ago:
Pikachu can learn Volt tackle when its IQ is high enough in the Mystery Dungeon games...

Although Ash's Pikachu did hax to learn Volt Tackle, may I remind everyone about the "Thunder Armor" created in the fight between Tate and Liza.

I just had this horrible thought.

Ash leaves pikachu for a few minutes, and comes back to a different pikachu, and accidentally takes it and leaves his original pikachu in some random place.

I have no idea why, but that idea immediately reminded me of a deleted scene from the movie Cars, where Lightning McQueen's engine was put in a steamroller while Mater borrowed the body. The media arrived and thought Mater was actually Lightning.

Now, if something like that happened with Pikachu, it could make a good filler episode.

Proof that Ash uses gameshark. :V

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