Pictured here is rock band ZZ Top playing the Little Cypress-Mauriceville High School senior prom in Orange, Texas, May of 1971. As it turns out, sometime between signing the contract and the date of the actual event, the band became huge. 

They actually tried to get out of it last minute but the school couldn't get anyone else and the band had signed a contract so they had to perform. So there they were, the biggest new rock band to hit airwaves, jamming out a paper streamer filled gymnasium for a graduating class of about 100 kids... until word got out and people were climbing through windows to crash a prom.