When I was a kid, I'd play We Three Kings in a sort of upbeat, fun way -- I liked the melody but thought the song was too ponderous. My mom would always say "What are you doing?" and make me play it right.
If only she'd known that encouraging my Christmas Improv might lead to my joining a moderately successful rock band someday:
Okay, it's only a small part of that song -- but still, I was on the right track.