Goofs

When Beavis and Butt-Head leave the motel room where they'd been locked up, the lights in the room are off. When Serena and the others enter the room moments later, the lights are on.

When the toilet paper arrives at the prison, three trucks are escorted by police, but four trucks back up to the facility.

While fighting inside their former home, Butt-Head punches Beavis, sending a spray of blood onto the wall near the door. The shot then changes and when it shows the wall again, there is no blood.

Beavis's hand is mangled in a garbage disposal yet is perfectly fine just moments later.

When the lieutenant governor tries to help Beavis and Butt-Head escape the motel, they exit room 16, which abuts room 17. When the angle changes, they are in front of rooms 14 and 15, then when the angle changes again they are once again outside 16 and 17.

Beavis and Butt-Head are shown to survive "several days" in their space suits but those only hold enough oxygen for several hours.

While in jail, Beavis eats from a baggie of unidentified pills. He eats many fistfuls of pills, yet the volume of pills in the baggie never decreases.

After the nacho stand worker shows Butt-Head how to pay for things with the phone, Butt-Head is briefly seen holding up a tray of nachos. Butt-Head is then empty-handed and the worker gives him the tray of nachos he was previously seen holding.

The track plate for the chain lock on the motel room door is missing the end. If the chain were inserted into the track and the door opened, the chain head would slide right out.

This isn't a mistake. It's faulty security equipment.

When Beavis and Butt-Head are following the van in reverse, one of the federal agents suggest they might be East Germans, who trained their assassins to drive backwards to give their snipers a better field of vision. This part of the movie explicitly takes place in 2022, by which time East Germany hadn't existed in over 3 decades.

In Beav-Butt-Verse, there are still East German trained sniper/drivers around.

It makes no sense that Beavis and Butt-Head should be able to change into their space suits more quickly than Captain Serena. Or at all.