[The_Return]

I'm going to - and this hurts me more than you know - agree with Ferret on this one: scare the little bastard.

I'd leave the bat at home though...I know if it was me, that'd just be way too tempting. What you should do is go up to him all friendly-like, put your arm around his shoulders, and casually and subtly theaten him - make sure you're smiling the whole time. He'll never go near your friend's sister ever again.