Blockbusters/Funny

Bill Cullen: Listen carefully, "F" question coming. What "F" is an incident which gets big laughs and its own subpage on the website All The Tropes?
(buzz-in)
Cullen: You, reader over there, for the game.
You: Funny Moments?

Cullen: That's right!

Bill Cullen (1980-82)

Several dozen, some of which are shown here, here, and here. Some of those listed below will refer to these.
The time "X" got welcomed to the main-game board (Video #1, 3:30). The game began with that letter pre-selected, and went through three questions before somebody managed to buzz-in.
A choice of "D" when it very clearly wasn't going to do anybody any good (Video #2, 3:05). Cullen, of course, had a ball with it all the way through.

Cullen (after the first question is missed): Another D question coming, and I caution you all the answer is very, very unimportant.
Cullen (after the second question is missed): You know, I'm getting almost as many Ds here today as I got in school.

An "E" question during Leland Yung's first reign (Video #2, 5:50) — "What E would a doctor be examining if he was using an Otoscope?" Although Yung gave the correct response, Cullen thought he said liver.

Cullen: Well...if the Otoscope is long enough, there's nothing impossible!

An episode during Yung's return visit (after the set changed to the blue backdrop) had an incident (Video #3) in which one of the lights on the board had gone out; Cullen implored the young viewers to get out "mommy's lipstick" or "mommy's nail polish" and color in the blank spot. Once the game was finished, he told the viewers to rub off the red spot with "daddy's wristwatch".
After Bill made an Incredibly Lame Pun (Video #3, 2:03), the person in the sound effects booth played the Losing Horns that normally played after someone lost the Gold Run.
On another episode (Video #3, 4:02), Bill threw a question down the "hole" before he finished reading it; not only did he finish reading it, he also noticed some old yellow cards from Jeopardy! — and even Art Fleming.

Bill Rafferty (1987)

One contestant, given the question "What 'A' is the part of the body where the first thermometer invented for clinical use was placed to get a reading?", answered "Anus." Rafferty got in the last laugh when he pondered how the discussion went when they wanted to change places: "You wanna put it WHERE?!?"
On one episode, Bill accidentally consoled a losing contestant with "Thanks for playing Card Sharks."

British Version

One contestant rang in with the Freudian Slip of "orgasm" for "What O means any living being?"
The "Kama Sutra" answer.