Because we are complicated, our wedding invitation was idiosyncratic. Letterpress, with hand applied watercolor to pick out the green in the intertwined letters. And a dictionary definition of marriage: "the combination of the king and queen of the same suit, as in pinochle".
Needless to say, we did not include a preprinted RSVP card, because I believe that everyone ought to know how to respond, properly, to an invitation (and, furthermore, that thank you notes are to be hand-written and put in the mail).
My absolute favorite response was from a dear, crusty, across-the-street neighbor. If memory serves, it was the first response we got, and it was perfect.
Happy nineteenth anniversary, dear.