Mel Brooks wrote those words.

IIRC the morons line was ad libbed by Gene Wilder, not scripted.

Given the reaction from Cleavon Little I could fully buy that it was an ad-libbed line.

Then again, they are actors. It might have started as ad-libbed, but entirely possible it had multiple takes still to get it "just right".

Did Mel or Richard write this part?

Do you attribute the following to Yoda or Lucas? "Do or do not, there is no try."

Well, technically someone originally proposed them in some ancient PEI Ur language and then Mel rearranged them. But you’re right. I couldn’t remember Wilder’s character’s name and kept coming up with The Frisco Kid. The 70s were a great time for weird film.