When a strange purple fly bites one of the Smurfs, a full-on purple epidemic develops in the Smurf village! After being bit, a Smurf turns purple, all he can say is "GNAP!" and he goes berserk! The purple Smurf runs amok through the Smurf Village biting other Smurfs on their tails, causing them to turn purple and act crazy too! Soon there are more purple Smurfs than blue Smurfs in the village. It's up to Papa Smurf to find a cure and save Smurf Village...