Deliberate mistake: When Alice jumps on the dog and they start running, her dress and her hand-band suddenly changed side. Probably they mirrored the image, and instead of going left as directed, it felt more accurate to go right.
Deliberate mistake: During the fight with Roxy (evil ex number 4), she falls forward before Ramona's leg hits her.
Deliberate mistake: There was no possible way for Edith to still be alive after the spiked coffin closed in on her. There are spikes on the doors and at the very back and sides of it, and she couldn't have squeezed in to brace herself. Probably done for obvious reasons, but still a mistake nonetheless.
Deliberate mistake: When Gale and Lucy see the Blue Star for the first time on the Volcanic island, on the second shot of the beach, the sea and the boat and star, the view from the beach, it is a still picture, the waves are not moving. All of the characters are moving but the sea is perfectly still.
Deliberate mistake: When Gulliver is first placed in the dungeon, he is attacked by a tiny seagull, however comparing the size of the bird with Gulliver's foot, it appears to be about the size of a fully-grown Lilliputian. This was obviously done deliberately as a correctly-sized seagull would be far too small for the joke to be effective.
Deliberate mistake: All Minor Hockey Leagues in North America require players to wear visors with their helmets.