‘Do your bit’
Chris Nashawaty wrote perhaps the definitive book about the movie. It’s called simply “Caddyshack”.
Thanks to the book, we learned that Rodney Dangerfield earned a mere $35,000.
We also learned that the long-time comic wasn’t used to being on a movie set. Ramis would call out “Action!” to no avail, as Dangerfield didn’t respond. This happened a few times until finally, Ramis told Dangerfield “Do your bit.” The first scene they shot was the one in the clubhouse. Dangerfield sprang into action when he heard “Do your bit” and even perfectly ad-libbed the “free bowl of soup” line. From then on, Ramis simply told Dangerfield “Do your bit” instead of saying “Action!”