> I would imagine it looks something like having a housemate randomly stuff the cat into one of two bags and you randomly opening precisely one each night via some sort of complicated-but-scientific mechanical contraption.

I dasn't - I'd be accused of being a sociopathic animal abuser (again). On the other hand, there must be some way to rig the door to open at, say, 1 AM with 1:1 odds. Hm...