Primeape Goes Bananas - S1-E25
Corrected entry: When Ash is talking to Professor Oak, the latter tells him that Gary has already caught 30 pokemon. But in the episode Mystery at the Lighthouse (Season 1, Episode 13), Oak said that Gary had already caught 45 pokemon.
Correction: The episode aired out of order due to controversy caused by an earlier episode. Not a mistake due to the Pokemon being correct in the order it is supposed to be in. On DVD releases, the episode is placed correctly.