Most Helpful Guy
I know its inappropriate... but when a guy in that age range does something like that, its called "testing the waters". He wants to know how far he can go and get away with it. If you didn't like that he spanked you, then tell him and he will draw the line there... it you liked it and didn't mind, next time you see him, return the favor.
(mind you, returning it may need to testing again)