It's against my better judgement to post this, but...

That telegraphs the answer rather than adding punch. "What's Delaware" belongs to the same class of jokes as "What's a Henway?" (a few pounds! ha! ha!) in that the way in which the question is posed is intended to throw off the listener. Adding "to the party" to the above makes it obvious that we're no longer talking about the state but rather punning on its name.

And now, having explained the mechanics of the joke, it is dead, dead, dead. Let that be a lesson to you.