What was Philemon's funniest joke that had to do with a goose and a lawyer?

What can a goose do, a duck can't and a lawyer should?

Stick his bill up his butt.

Another answer is this:

"Philemon's joke doesn't translate from Greek to English (and across the centuries) very well. It's sort of a combination of you-had-to-be-there and nothing." -Bart King in an email.