31 favorite monsters: the purple fly
I watched a lot of the Smurfs when I was little, but I never remember seeing the one with the smurf-sized zombie apocalypse. As an easily frightened child I may have just blocked it out, because it's honestly pretty damn horrifying by kid standards. The purple fly is seen only briefly at the start of the episode, but bites Lazy Smurf on the tail and begins a surprisingly disturbing epidemic; Lazy turns purple, starts hopping everywhere, can only shout "g'nap!" and takes every possible opportunity to bite his fellow smurfs, transmitting the mysterious infection. Everything goes back to normal in the end, of course, but not until they've made sure that every little kid in the audience is having nightmares tonight.
Interestingly, this episode was adapted from one of the original 1960's Smurf comics, but formerly involved a plague of mindless black Smurfs. You can guess why they decided to go with purple - the same reason they went with purple for the formerly black-faced Pokemon, Jynx. So remember: all purple cartoon characters are just veiled jabs at black people.
Watch the full Purple Smurfs cartoon here.