Variant of Colt's "something that makes you happy and sad at the same time" joke

... A man says to his wife, "I bet you can't say something that would make me both happy and sad at the same time."

The wife thinks for a moment and responds "You finally get to try anal tonight! I'll get the strap on."

*Edit* As PM'd by a member or two, pegging isn't seen as sad, just as pure happiness. So I'll change the wife responding "I am pregnant and we are having a baby, but it is not yours."