It's kinda ridiculous if a guy is wearing panties. But if he is doing it as a joke because his girlfriend thought it would be funny than who am I to judge. And I guess if your penis is really small (I am not pointing any fingers here ;)) it might actually be appropriate.
Question 16: Have you ever worn a any other kind of female clothing (bra, pantyhose, high heels, etc.)?
A1: No, I'm not a sissy! --> 1 Point
A2: Yes, as part of a costume (or a dare). --> 3 Points
A3: Yes, and I still remember how excited I was and how good it felt. --> 5 Points