Continuity mistake: When they are in the Whitehouse, and Beavis has turned into Cornholio, he picks up the "Red" hotline phone on the President's desk, and is talking to the nuclear bomb officials. Later, when they are in the President's office again, getting their certificates, there is now a black phone on the desk, where the red one was. (01:03:05 - 01:11:00)
Continuity mistake: As Beavis and Butt-head are dancing in the casino the floor is just flat and one surface. In the overhead shot of them dancing you can see part of the floor has changed to an tiled area instead of a plain flat surface. Also there are a number of people sitting at tables just in front of them whilst dancing. In the overhead shot they and the tables have disappeared. (00:21:30)
Continuity mistake: When Muddy pulls up after dropping off Beavis and Butt-head, the front tires go over the curb. In the next shot, when Muddy gets out of the car, the front tires are a few feet back.
Continuity mistake: After the highway accident and the FBI agent's asking his assistant where the bus was headed, he tells him it was headed to DC. In one shot the assistant's right hand is on the desk, but in the next one he's flipping through some papers. (00:55:40)
Continuity mistake: When Butthead slams in Anderson's Truck after he falls out of the trunk, the truck crashes and is wrecked in the front, but when you see Beavis walking towards the Whitehouse, Anderson's truck drives by and it is in perfect condition. (01:01:31)
Continuity mistake: From the point where Muddy is introduced in the movie to the point where he drops Beavis & Butthead off at the airport, he takes eight swigs from his whiskey bottle and yet the amount left in the bottle never changes. (00:09:45 - 00:12:35)
Continuity mistake: When Beavis & Butthead are walking off with the school's AV equipment, when they get to the outside steps, you can see that they are not dragging any equipment behind them, when they were doing that just a couple seconds before. Oh, and the equipment they were dragging with them does show up after the whole unit falls down the outside steps. (00:05:50)
Continuity mistake: When Beavis & Butthead are walking at night looking for their TV, Beavis is seen with a remote control clicking it into nothing. When they get to motel and start pounding on the doors, Beavis no longer has the remote control. (00:08:45)
Continuity mistake: There are no bongos in the song "Love Rollercoaster", yet in the casino scene in the movie where the song is played, the band has a bongo player. (00:19:25)
Suggested correction: It's not unusual to add extra instruments on live performances. Sometimes whole orchestras are added in rock songs when performed live.
The RHCP version heard/used has no bongos. And it's not a live version, nor have they ever performed the song live.
Continuity mistake: The first time the old lady shows Beavis her bottle of "no drowz" pills, the upper left writing on the label says "Safe as coffee", but when she shows him the bottle later in the film, the same writing says "No caffeine"
