Other mistake: Near the end of the closing credits, when the Warner Bros. Copyright appears, you'll see the very first word "All" spelled incorrectly as "Al" in "All material is protected by Copyright Laws of the United States and other countries throughout the world." (01:26:40)
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)