Caption Contest 79: Ride 'em, cowboy!

With many thanks once again to the inestimable "Glenn3", whose "Say What? Pictures" keep me well stocked with Funny, your challenge for this week is to come up with the funniest replacement dialog for the following random comic book panel:

Leave your entry in the comments to this post by next Monday, at which time I'll pick the funniest one, the author of which will receive his or her choice of either any item they like, or a portrait, to be included in the final HeroMachine 3 version.

Good luck everyone!