“...after she confronted him over tweaking the script...”
IIRC, Bill was to have just a bit part in Caddyshack. But he adlibbed all of his lines and they just kept going with it.
He did that in Scrooged too.
Here he is in Little Shop of Horrors, the dentist scene.
https://www.youtube.com/watch?v=XB7R0ZxNgC4