1 He's stopped being cheap since I told him he was stingy. 2 Fine 3 Both are fine - ususally, 'what episode are you on' might imply that the person is currently working/watching, whereas 'at' could imply that they are having a break from the activity. 4 I hate people seeing me do that, or, I hate it when people see me do that. 5 Fine 6 Which tooth