What should I write for..?

So I'm sending rehearsal dinner invitations...I know you don't really "need to" but I figured it wouldnt hurt! So on the RSVP spot I want to kind of reinforce that we neeeeeeeed them at the rehearsal( we have a couple people in the wedding party who might just see it as an optional thing!) but I'm trying to think of a funny way to word it? I dunno any help would be great!