At the start of the road race, the starter has a green flag. When we cut away to the stock footage, the starter has a red flag.
During the race scene, Eric Von Zipper is riding motorcycle #13 when he wipes out in the grease he's riding #21 and then a few seconds later he's back on #13.
When Von Zipper sings on top of the pool table, right before he falls through the table a quick cut takes us from a blue felt topped table to a green felt topped table, which likely had been swapped with a table top rigged to break. But the felt color clearly changes.
During "That's What I Call a Healthy Girl," Johnny appears to play a guitar solo, but he's just strumming the instrument, as if playing rhythm guitar, instead of playing the actual melody.
One of The Kingsmen is plucking a white guitar as if it's a bass guitar, but it's a six-string guitar, like the other guitar player is using.
When Mickey Rooney first appears, the surfers ask his name. He replies, "J. Peachman Keene" instead of Peachmont.