Zombies

Zombies are reanimated walking corpses that are commonly featured throughout the Treehouse of Horror Series

In Treehouse of Horror
Zombies first appeared in the Treehouse of Horror halloween episodes in the Treehouse of Horror III short "Dial Z for Zombie". In a story told by Bart Simpson, Bart brings the dead back to life with a supernatural curse while trying to help Lisa resurrect Snowball I. The zombies travel across Springfield eating brains and turning many people into zombies. When the zombies break into the Simpson's house they attempt to eat Homer but consider him brainless. When Bart and Lisa think of a plan to reverse the spell the Simpsons head down to Springfield Elementary School where Homer kills various zombies. Eventually, Bart reads the spell and the zombies return to their graves.

In Treehouse of Horror IV, the couch gag involved the Simpsons family digging out of the floor of the living room as zombies. In the Treehouse of Horror XIII short "The Fright to Creep and Scare Harms", Billy the Kid and several other wild west outlaws rise from the dead and terrorize Springfield (but they were possibly lich's as they were more inteligent enougth to know who they are), which just outlawed the ownership of all firearms. when billy and his croonie's lay wast to the town homer goes back in time with frinks invention to re kill the zombies ,

In the Treehouse of Horror XX short" The Fright to Creep and Scare Harms", the citizens of Springfield get infected by eating burgers tainted with a virus that turns them into zombie-like creatures called "munchers". Unlike previous predecessors, in this case the zombies were similar to those in the movie 28 Days Later (the Halloween short even contained the subheading "28 days later".) bart was ammune to the disease and could be the key to the cure, they try to sneak out of springfield only to attract more zombies. after the "munchers" deystroy the house a gun wielding rhiner wolfcatsle breks down the door only to be killed. while the unhuman hord is distracted the simpsons are lead out by apu ( who wasent infected as he is a vegitarion), after a drive through the city and apu is killed. homer was bitten but before bart could kill him they make it to the safe zone, after a moment of confuseion involveing eating bart , the zombiefied citizens are cured becuse all bart was to do was take a bath in thier soup.

The Simpsons: Hit and Run
In the final level of The Simpsons: Hit and Run. As part of Kang and Kodos's plan to bring up the ratings of their show "Foolish Earthlings", tainted Buzz Cola is poured into the waterways of Springfield, which seep into the graveyards of Springfield and wake up the dead. Throughout the last level they are seen walking around Springfield. Strangely, the Zombies do not attack Homer, but the radio describes them attacking Springfield Stadium. After Homer blows up the UFO, it is assumed that the zombies were killed.

Trivia

 * Zombies in the Treehouse of Horror series were caused by three things: Supernatural events (The short "Dial Z for Zombie" in Treehouse of Horror III and "The Fright to Creep and Scare Harms" in Treehouse of Horror XIII), man made experiments ("Frinkenstein" in Treehouse of Horror XIV) and disease ("Don't Have a Cow, Mankind" in Treehouse of Horror XX). In the Simpsons Hit and Run, zombies were caused by alien experimentation.