Corrected entry: Pay close attention to the scene in the airplane where Butthead is behind one of the flight attendants in the aisle as she is serving dinner. He says, "Hey, I got a beer, want some?" A split second later, we see Beavis rush the cockpit and scare the pilots. At this exact moment, we now see Butthead at the back of the plane with that same flight attendant (same hair, clothes, everything), only she is seated in one of the take off seats and reading a book. Even if for argument's sake, Butthead did walk to the back of the plane, that same flight attendant couldn't have been there.
Corrected entry: After the power goes out in Las Vegas, Muddy is questioning the hotel clerk. The clerk says "They got on some bus...probably heading west." Well west of Las Vegas leads to the Pacific Ocean, not Washington D.C.
Corrected entry: In the scene in the car going to the airport, Muddy explains that the boys are to get back a satchel for him. When he demostartes how big it is, the whiskey bottle in his hands magically disappears and reappears.
Corrected entry: When Beavis & Butthead are walking out of the hotel room to get on the bus to go to Washington DC, Beavis doesn't have his shoes on, but when he is outside, the shot shows him with them on.