Remus Lupin

It's better than nothing.

Spending so many years trapped and helpless in a dormitory room with you and James, I could hardly help finding myself indoctrinated into the creed 'If in doubt, prank it!'

I was still far better behaved that either of you, of course. I have the prefect badge to prove it.

If there's any connection between Walden and Quirrell, I'm sure I don't know, and if I did I probably wouldn't say. I only wanted to mention it as he's likely to be in the forest later, and may be able to confirm whether I am, as suspected, going senile in my old age.