Puns involving substitution of meaning

Posted by David on January 18, 2004

I'm trying to come up with a birthday card based on variations of punning phrases. For example, 'How long is a piece of string?' becomes 'How long is a birthday?' The answer will be 'Longer than a piece of string.' There's a substitution involved in making the pun.

Similarly, the pun 'Time flies like bananas, fruit flies like an arrow' involves substitution. This pun works because it confuses one meaning of a word with another. I'm trying to think of other words that I can do this with, to create a birthday card that's a series of questions (How long, how far,...) whose answers involve play on those words.

Any suggestions?