|“||You'll pay for this! With your childrens' blood!||„|
|~ Willie vowing revenge for his death by killing the parents' children.|
|“||I'll strike where you cannot protect them! In their dreams!||„|
|~ His last words before turning into dust.|
Groundskeeper Willie, although seen as a benevolent character in the regular episodes, serves as a minor antagonist in The Simpsons' Halloween special series: Treehouse of Horror.
He appears as the sole main antagonist in the second short of the sixth episode.
Appearance in the special
Bart has a nightmare that Groundskeeper Willie is out to kill him. He is slashed with a rake, and the scratches are still on his body after he wakes up. Many other students at Springfield Elementary School also say they were terrorized by Willie in their nightmares.
When the students take a test, Martin falls asleep and is strangled to death by Willie in his dream, before waking up and dying in the real world. Bart and Lisa tell Marge about the incident. While she at first denies that she knows anything, Marge eventually tells the kids the truth: Willie was set on fire in a furnace explosion (caused by Homer, who had increased the temperature of the school's thermostat, ignoring Willie's orders not to) and burned to death while the parents of the students looked on and did nothing. Angered by the parents' stupidity and callousness towards his screams for help, Willie told the parents he would get his revenge by killed the children in their dreams, where the parents cannot protect them. At first, the parents ignored this, but even in death, Willie made good on his promise just like he did to Martin.
Upon learning this, Bart, Lisa and Maggie try not to fall asleep for several days, but eventually Bart decides that he is going to have to go to sleep and fight Willie in his dream. Lisa is supposed to stay awake and wake him up if he seems to be in trouble. Bart falls asleep and attempts to find Willie, who appears as a lawn mower. Bart manages to trick Willie into mowing a sandbox containing quicksand, and Willie sinks. Bart then says he can get back to his regular dreams, him and Krusty winning the Super Bowl, but Willie turns into a giant bagpipe spider and is about to kill Bart when Lisa enters, trying to wake him up.
Bart realizes that since she is in the dream, that means she has also fallen asleep. At that point, Willie grabs Lisa, intending to killed her too. They are about to lose the battle when Maggie appears and uses her pacifier to seal the vent on Willie's spider-body, resulting in Willie exploding that. In the end, much to the kids' relief, Groundskeeper Willie is shown to be back to normal of the next day. He comes out of a bus and tries to intimidate them by making noises and faces, but then he forgot his gun on the seat to kill them, so he chases after it, dropping one of his shoes.
- This is the only time so far Willie was a villain. Throughout the rest of the series he is portrayed as a gruff but ultimately benevolent character.
- This version of Groundskeeper Willie is obviously a parody of Freddy Krueger.
- Much like in his appearances in the other shorts of Treehouse of Horror VI, Willie ends up getting killed in the climax.