Other mistake: Go to the Day-Care Man. When he asks you if you want him to care a Pokemon for you, answer YES, but in the Pokemon list, press B to cancel. He'll say "All right then, Come again." However, the "Come" shouldn't be capitalized, it should be "come". This happens because this is a shared text, so when you answer NO to his question, he'll say "Come again", and that's why it is capitalized for this text. However, it is still a mistake. This was made due to a similar text error in Red/Blue, but this mistake was created.
Bug: Go to Bill's house. Before you enter the door, watch quickly at the back of his house. You'll see a mountain without the usual border.
Other mistake: At the beginning of the game, Oak gives you a Pikachu. By this time, Pikachu is in a Pokeball. When you fight against Gary, however, the Pikachu doesn't come out of a Pokeball, like in the rest of the game. However, in this battle, he should come out of his Pokeball.