How about "TransTastic!"
or... "Is she or isn't she? Only her surgeon knows for sure..."
or... "Maybe she's born with it. Maybe it's Maybelline" (okay, I couldn't figure out a good takeoff on that one. Maybe someone else will do better).
I saw a lot of really GREAT T-shirts at last year's Pride festivities. My favorite one was:
"Let's get one thing straight. I'm not."
I am DEFINITELY going to this year's Pride, and this time, I'll be Myself. Last year I wasn't even out to myself yet.