The episode starts with Beavis and Butt-head watching a horror film, when two kids trick-or-treating show up at their door. Mistaking them for handing out samples, Butt-head takes their candy and slams the door in their faces, and soon their father takes it back and beats them up, too. They decide to go out and trick-or-treat, but are dismissed twice for not wearing costumes. First Beavis jokes around, he puts on a winger shirt and sings the song "Seventeen." This irritates Butt-head. Then Butt-head suggests they dress up as ghosts. However, when wearing the white bed sheets, Beavis complains that the sheets smell funny. Butt-head reveals that they are his "special monkey sheets". Beavis knows exactly what he means. So he immediately reacts in disgust trying to take it off as Butt-head laughs. Then finally Beavis puts his underwear over his head and calls himself a nad. Butt-head pours melted cheese all over himself and calls himself Nachos.
They first approach a house where a kind man doesn't give them any candy. He instead gives them pamphlets for some scary reading. Next they approach Anderson's house, who is about to dismiss them when his old friend calls, and he leaves his living room. Beavis and Butt-head go inside, where Beavis starts eating all of the candy in the candy bowl. Butt-head demands he give him some too. But Beavis refuses to give him any and quickly eats more. Then Beavis gets hyper and transforms into Cornholio. Then another kid comes to the door saying: "Trick-or-treat". Beavis makes a vicious face to him and loudly screams at him and scares him away. Anderson comes back and kicks them out, and when another trick-or-treater comes to Anderson's door, Anderson yells at him, mistaking the child for Beavis and Butt-head. Beavis and Butt-head then wander down the streets until Todd nearly hits and beats up Beavis.
Todd puts Butt-head in the trunk of his car and drive to the Country and drops him off on the Crazy Farmer's farm. Beavis, resumes wandering around. The soon he encounters Stewart and AV club friends. They are about to T P houses. Beavis' hyperactive Cornholio persona creeps them all out. He demands Stewart to give him his roll of T P. Stewart and his friends give him the T P and run off. Then Beavis stuffs some toilet paper up his crack and walks around with the roll of T P hanging from his shorts. He then runs into another young trick-or-treater. He demands that he give him his candy, but he doesn't want too. His Cornholio persona really creeps the boy's mom and dad out. So the boys parents persuade him to give him the candy and they all run off.
Eventually he winds up at the Country, and meets the crazy farmer, who is digging a hole. Beavis is next shown hanging from a meat hook. Just then, a zombified Butt-head and the crazy farmer walk in. They both pull out chainsaws and slaughter Beavis. Beavis screams his head off in fear and unbearable pain as the screen slowly turned red and ends.
While Cornholio (Beavis) is wandering around the graveyard searching for candy, a kid is dressed up as a Red Ranger from Mighty Morphin' Power Rangers (a cultural reference). The family gave up their candy and ran away.
The 'Butt-O-Ween' title is a parody of the 1978 movie, Halloween. Interestingly enough, this special aired the same year as Halloween: The Curse of Michael Myers hit theaters a month before.
This episode aired on the actual day of Halloween.
Three days ago in the Beavis and Butt-head world was Beavis' birthday.
In this episode, Cornholio finally gets some T.P. for his bunghole.
A scene where Beavis wears Stewart's Winger shirt and says "I'm a wuss" before singing Winger's "Seventeen" appears in airings but not on the VHS or DVD releases.