My Babysitter's a Vampire - Season 2 Episode 11 Halloweird

Ethan's nerd-fest Halloween party takes a turn for the dangerous when Rory's magical mask transforms guests into the real-life versions of their costumes. Ethan, Benny and Sarah have until midnight to reverse the spell, or the transformations will be permanent. Sounds easy enough... until they realize that their party guests now include an insane supercomputer, a gorilla, a half-dolphin ninja, and Erica - who just wants peace and quiet to practice a 'traditional' True Vampire Halloween. Oh… and Ethan's Mom comes home early from her own party, with a witch costume that's very convincing…