On an episode of the game show "Common Knowledge" (hosted by 'N Sync member Joey Fatone) The question was:
If you're learning how to do a "Harold" what kind of class are you in:
A. Sewing. B. Improv. C. Glass blowing
The answer was B. Improv. Joey explained that "Harold" is a long form improv format that gets its name from a joke in The Beatles movie "A Hard Day's Night."
I think maybe they were referring to the "What do you call that haircut?" and George says "Arthur." joke. I can't think of a time anyone says "Harold" in the movie, can any of you?