Continuity mistake: In both "Attack of the Prehistoric Pokémon" and "Charizard Chills", Charizard carries Ash on his back without any trouble. However, later on in "Charizard's Burning Ambitions", Ash is suddenly too heavy for Charizard to carry.
Continuity mistake: In the early episodes of the Advanced Generation series, May is portrayed as being slightly taller than Ash. As the series moves on, May is consistently portrayed as being slightly shorter than him.
Answer: There are a lot of fan theories around this, but the most common theme is that Pikachu had another trainer before Prof. Oak, who gave him to Ash. Pikachu didn't appreciate being handed over.
Ssiscool ★