Other mistake: When Dorthy is trying to audition for the Muppet's the man says they are gone and the Muppet's bus pulls up. If you look when the bus is pulling up there is no one in it, even the driver seat is empty. Then a few seconds after the bus stops Kermit and Miss. Piggy come walking out.
Other mistake: Right after Dorthy and Pepe crash and the trailer is all messed up; Dorthy gives Pepe a teddy bear's clothes to put on. Everything is fine with that except Pepe puts it on and he has four arms and they all have sleeves and you can see when Dorthy gives it to Pepe the bear has two arms.