Said in an extremely disparaging voice: "You guys have a whole society for Tolkein?"
"So are you and the CS Lewis club like, rivals?"
"What did Frodo say when he saw trees dancing? That's Ent-ertainment!"
"No offence, but this seems a bit... lame."
"So do you have any members?"
"Do you guys dress up and swordfight?"
And my personal favourite:
"What's a Tolkein?"
(Of course, nearly everyone was very nice, and by the end of the day there were 60+ signups, and 100+ termcards handed out. Not bad for the first day, although my feet are now killing me!)
Edit to add: Over the three days total we got just over 200 signups! Which means we'll need about four of the room we actually have for freshers' moot if they all turn up... however, that's doubtful ;)