When people tuned into Happy Days 51 years ago, they witnessed a dark moment in sitcom history, and now a Fonzie fan theory might finally explain it.

WAUKESHA - Fifty years ago, Waukesha's 15 minutes of prime-time television fame came unexpectedly, and certainly repetitively, in the first Christmas-season episode of the TV series "Happy Days." ...

The first assistant director ... One week, they even had to shoot two episodes in five days to stay on track—nothing happy about those days! The grueling pace wasn’t the only challenge.

ABC Photo Archives/Disney General Entertainment Content via Getty Henry Winkler smouldered as Fonzie while relaxing in Al's Diner in an episode of Happy Days in 1975.