"The Big Bang Theory" is an American sitcom revolving around geeky room-mates Leonard (Johnny Galecki) and Sheldon (Jim Parsons), their beautiful neighbour Penny (Kaley Cuoco) and their socially awkward friends Howard (Simon Helberg) and Raj (Kunal Nayyar). Penny guides the boys with invaluable lessons about social interactions with women, while they teach her about video games and comic books. Sheldon prides himself on his superior intellect and constantly looks down his nose at everyone else. One of the recurring themes in the show is Leonard and Penny's on-off relationship. Howard stopped having fantasy relationships with women when he met Bernadette (Melissa Rauch), and Amy Farrah Fowler's (Mayim Bialik) sexual frustration is clear for all to see because she has feelings for Sheldon that are never going to be reciprocated. Recurring characters include Howard's overbearing mother, Mrs Wolowitz (voiced by Carol Ann Susi), who is heard bellowing out but never seen, and Stuart (Kevin Sussman), who runs the comic-book store frequented by the boys. The hugely popular series premiered on Channel 4 in 2008.