Sheldon is often described as a stereotypical “geek”. He is usually characterized as being extremely intelligent, detail-oriented, eccentric, and occasionally disturbing. Despite his intelligence, he often displays childlike qualities, such as being extremely stubborn and a lack of common sense. It is claimed by Bernadette that the reason Sheldon is sometimes unpleasant is because the part of his brain that tells him it is wrong to be nasty is “getting a wedgie from the rest of his brain”, although, in season 8’s “The Space Probe Disintegration”, Sheldon tearfully admits to Leonard that he is aware of his peculiarities and how his behavior comes across. The first four episodes of The Big Bang Theory portray Sheldon slightly inconsistently with respect to his later characterization, in which he is depicted as rather witty and sarcastic, and slightly flirtatious towards Penny in the pilot episode: according to Prady, the character “began to evolve after episode five or so and became his own thing”.