Yes the panties, Sirius should always have them on. I quite agree - it's a kink of mine!
Littlemissgg wrote a great fic in which Harry was hiding in a wardrobe spying on R and S and Sirius was making Remus wear his glasses and do the whole "Professor Lupin thing." It included the fabulous like, "Come all over me, Professor Lupin." Gotta love that!