A Vandergrift Casino Theatre prank used to make freshman stage crew people go insane trying to find out how to "jimmy-up the mack". Bottom line: the "mack" that needs to be "jimmied-up" does not exist!
Cast member: "Go jimmy-up the mack, Bob"
Bob (first year stage crew): What the heck is a jimmy-up the mack!
Cast member: Just go do it!
Bob: What is it!
Cast member: The show will be ruined if you don't jimmy-up that mack! Now go!