Revealing mistake: When King Koopa tells Dr. Sheldon to make a potion that will stop Princess Toadstool, he is briefly layered between a podium and a bag. (00:12:28)
Continuity mistake: When Butterfingers urges Princess Toadstool to stay, her leg bracelet disappears. This also happens when they run away from King Koopa. (00:12:14 - 00:14:34)