I've sometimes had an inkling that some comedians have scripted fake fluffs in their shows. I particularly accuse Red Skelton of this, since Red's retorts seem to flow a little too smoothly. (I don't doubt that he was a great comedian, but his comebacks seem somewhat wordier than what would be natural.) I don't have any proof of this for Red, BUT...
I was listening to Jack's New Year's Show of 1944/45 and heard Phil throw something in about his drinking, and then Jack muttered something about "that isn't even in the script!" As I have mentioned elsewhere on this forum, I love to look at old scripts to see what makes things tick. Also knowing that a lot of what is available has been corrected to show what actually went out over the air, I was anxious to see what was penciled in. I went out to tobbaccodocuments.org, (having now changed my mind about the negative impact of our litigious society,) and got a shock. The whole thing was scripted!!
Check out the episode of 12/31/44 around 9 minutes in, and check out this amazingly executed "ad lib." It sounds completely off-the-cuff.
here is the script:
http://tobaccodocuments.org/atc/1432894 ... .html#p303