First of all, how Remus can go from that loving, wonderful night with Sam to a lesson day with Teddy!!?
'Cos he's Remus? And gets stubborn about sticking to promises at the worst times, usually? Heh.
Shopping for sex toys is pretty normal for these two, which is pretty frightening in its own way. Remus has managed to end up with a very complicated life here right now; the ordinary single father who works in a bookshop is really not so ordinary after all.