(55$ LC): Call this donkish overbet?

I think that you're wrong--- there is a very good reason for him to make this bet.

You called.

That's exactly the reason why a bet like this is sometimes very good. Against good players, I don't make this kind of bet... against an unknown player, I will frequently make a very odd bet-- because it triggers a disbelief in my opponent.

I like this move... if there had been more people in the hand, it would have been brilliant.