Continuity mistake: When Misty tells Ash that they should take a break, her bag disappears. This also happens when she says that they may be on a deserted island. (00:02:28)
Continuity mistake: When Ash allows Misty to have a break, there is no tree in front of the tree behind Ash that is closest to him, but in the next shot, there is. Also, Ash's head is turned, but in the next shot, it is not. (00:02:35)
Continuity mistake: When Ash tells Tracey to watch out, the strap on Misty's bag disappears. (00:06:30)
Continuity mistake: When Team Rocket is eavesdropping on Ash and his friends, Meowth does not have a lei, but in the next shot, one appears. (00:09:06)
Revealing mistake: When Ash tells Lapras to go back to the ocean, his left arm is transparent. (00:14:18)
Revealing mistake: When Ash's friends run over to him, as he dives into the pool, Pikachu can be running in midair. (00:14:27)
Revealing mistake: The pedal James presses when he slows down the lorry is the same one he used when speeding it up. This is due to the shot of him slowing the lorry down being a recycled shot of him speeding it up. (00:18:35)
Continuity mistake: Right before Tracey says that Ash is heading towards a cliff, Pikachu's tail turns completely yellow. (00:19:13)
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 ★