"In Anchorman, during the Sex Panther scene, Paul Rudd was determined to make Will Ferrell laugh and break character since it was always the other way around. He thought that this would be accomplished with the "60% of the time it works, every time" line. Will fired back with "that doesn't even make sense" line without skipping a beat once again making Paul/Others break character yet again."
"The famous scene of Vito Corleone holding a cat was not scripted. He just found a cat."
https://www.imdb.com/name/nm0778734/