That'd Be the Butt, Bob

Example:
As told by Anonymous...

During a taping of The Newlywed Game, a popular '70s TV show in which recently married couples tried to predict how their spouses would answer personal questions, host Bob Eubanks asked a female contestant how her husband would respond to the following:

"Where's the most unusual place you've ever made whoopee?"

She answered: "That'd be the butt, Bob."

Example:
As told by Chris Patterson (U.K.)...

A newlywed couple were at their reception, where the DJ was playing Mr & Mrs. If you're not in the know, Mr and Mrs was a British TV game where one partner was asked questions about the other whilst they were out of earshot, and then the question was repeated to see if their answers matched.

The DJ was asking the groom all sorts of questions such as "Which side of the bed does she sleep?" and "What's her most disgusting habit?" when he came to the final question: "Where's the strangest place you've ever had sex?"

The groom started by laughingly replying that he had no intention of answering, until eventually, egged on by the baying audience, he replied:

"In the back of my car."

A huge roar of approval went up as the bride was led back into the room, to give her replies to the questions. The DJ went through all the questions again until finally he got to the last: "Where's the strangest place you've ever had sex?"
[br[ The bride started shaking her head and muttering "No way" as the crowd began to bay for a reply. Even the grannies and the old aunts were getting involved, pleading for the answer. Eventually the groom came over and gently took her by the arm saying "It's okay, honey, I told them."

"You're sure?" she asked, nervously.

"Of course, darling, I'm sure," he replied.

"Okay," she said. "If you're sure."

Then slowly, holding the microphone close to her chest, the bride announced to all their assembled relatives and friends:

"Up the bottom."