Okay, Miss S. How about this one... I'm a member of the Directors Guild of America. Of course that isn't a professional credential for a writer (that would be WGA), but I've had people (published writing people) suggest strongly that I include it in queries. Would you care?
Actually, since every literary agent wants to be friends with Hollywood folks, yes I would. Added enticement to reprsentation would be tickets to your next premier, and if you really want my attention, offer to cast me in your next movie with George Clooney. Oh, and Killer Yapp needs a speaking role too.