Jokes for a wedding speech

A wedding speech needs exactly one good joke, early, so the room relaxes and the speaker finds their voice. It must not be about the couple's past, it must work for both families, and it must survive being told by someone who is nervous and slightly overdressed. The jokes here are warm, short and about marriage in general, which is the safest ground there is.

Tell it, let the laugh happen, then say the kind thing you came to say.