Lost and Found - S4.E3

Muffy's cousin Mort returns to the store for another visit, but Muffy is lost. After searching the store for her they discover she has been captured by Herman T. Horrible, an intruder, who plans on using Muffy in his carnival of weird animals. So everyone tries to rescue her by pretending to be mannequins but they must be careful of his magic gas that makes anyone who breathes it compliant (that's how he caught Muffy). After they rescue her, they give him a taste of his own gas and tie him up until the police arrive.