Continuity mistake: At the end of the movie when everyone is in Wayne's basement, we see Benjamin painfully walk up to Wayne's house for each ending in the dark. When the scene changes to Wayne's basement for the first ending, you can see through the basement window directly behind them that it's broad daylight. This is especially easy to see when the equipment starts to spark.
Continuity mistake: When Wayne and Garth are on their way to the Alice Cooper concert they show the car from behind you can clearly see that Garth is driving and Wayne is in the passenger seat but when they cut back to the car from inside Wayne is driving and Garth is in the passenger seat.
Continuity mistake: When Wayne is interviewing Vanderhoff on his show. He takes the liberty of placing some humorous slogans on the back of the question cards. However, the one about goats returns to the front of the pile when the camera cuts to a more distant shot and Wayne puts the cards down.
Plot hole: When Wayne and Garth are trying to get Mr Big to hear Cassandra's band, they refer to when they spoke to the security guard earlier in the movie. They claim he said Mr Big would be in Chicago on Friday when he actually didn't - he never mentioned a specific day at all and just said he was travelling that way next week.
Continuity mistake: Near the end of the movie when Wayne is driving to Cassandra's music video there are a lot of cars right before the policeman pulls Wayne over to spoof Terminator 2. But all the cars are driving behind him and next to him are gone when the pulls Wayne over.
Continuity mistake: When Wayne, Garth, Cassandra and Benjamin are at Benjamin's apartment, The level of Cassandra's champagne when she is standing out on the balcony is low. Cassandra then walks inside and sits on the sofa, where the level of champagne in her glass is higher, without anyone giving her a refill. (this is from a video viewing)
Continuity mistake: When the group are in the diner and Garth notices his "dream girl" stacking plates of pie and cake in the display case, she can be seen placing a plate on an empty tray, then the camera returns to Garth. Moments later the camera is returned to his dream girl and the tray is again empty.
Deliberate mistake: When Wayne begins playing the "Excalibur" guitar, the clerk stops him and directs him to a "No Stairway to Heaven" sign. The problem is that the guitar riff Wayne started playing sounded nothing like "Stairway to Heaven" so the clerk had no reason to interrupt him. Evidently the intro to "Stairway" was actually played in the theatrical version of the film, but its exclusion in the home video release makes the scene rather dubious.
Add timeSerious B
Continuity mistake: When Benjamin is talking to Wayne and Garth about giving Vanderhoff a spot on the show in the first scene. On the left side of the end of the table there is a tray of nachos with dip and different kinds of drinks, then in the next scene when Wayne talks to Garth about selling out the nachos with dip are on the right side of the table and the drinks are gone.