I wish the guys would get together, in David's absence, and agree to not shave for the remainder of the series, just to make David the outcast again, lol
A good prank would involve one or two of the housemates as accomplices. Always funnier when someone has to act. I'd say get some back-seaters, like Cat, Sandra, Sam or Ryan; people who haven't had as much camera time. Make it a pseudo task.
I don't have anything right now apart for some stupid stuff like getting either Jake or Jason in the Diary Room and have Big Brother tell him that they have received numerous complaints for sexual harassment, while other housemates watch from the lounge and have to play along. Could have Ryan or Sam telling Jason "Well, I did feel like you were coming on to me". Nawww, stupid.