Doing comedy roles is not a cup of tea for Saif Ali Khan. But he had done great job (comedy) in 'Kal Ho Na Ho'. Now he is doing another comedy flick with Rani Mukherjee 'Hum Tum'. He is playing a role of cartoonist. He said, "I'd just be nervous then. I am not arrogant enough to crack up at my own jokes. The joke is made on the sets and then the audience reacts, so you don't really know how it went down until then. And you thought shooting funny scenes was a laugh riot all the way? Think again!"