Peep Show is a British sitcom starring David Mitchell and Robert Webb. The series follows the lives of two men, from their twenties to their thirties, who live in a flat in Croydon, London. Mark Corrigan (Mitchell), who has steady employment for most of the series, and his lodger, Jeremy "Jez" Usbourne (Webb), an unemployed would-be musician, are the main characters of the show. It was shown on Channel 4 from 2003 to 2015.

Characters appear in all series unless otherwise specified.

Mark Corrigan (portrayed by David Mitchell) is the miserly, vindictive owner of the flat (in Apollo House) that he shares with Jeremy. Mark is portrayed to be responsible, articulate (both in his inner thoughts and his outer speech) and intelligent, at least compared with most of the other characters. He is also pessimistic, unhappy and socially and sexually awkward. He had a miserable upbringing, and is terrified of his father, who is gruff and difficult. Not much is known of Mark's parents, except that they have remained married despite various marital issues (including infidelity and the fallout from when Mark's father's British Aerospace shares collapsed). Their awkward marriage may be the cause of Mark's own struggles with women, warping his understanding of what a healthy and transparent relationship should look like. Mark is a graduate in Business Studies from the fictional Dartmouth University, where he met Jeremy. He passed 7 GCSEs, and he has a love of history, especially ancient history—which he originally wanted to study at university, before being pressured by his parents into reading business studies instead. He often makes references to history, including Nazi Germany and the Second World War, in relation to events that happen in his day-to-day life.

Mark is convinced that Jeremy's laziness, lack of logical rigour and indifference towards cultural pursuits are markers of low intellect, but often looks to him for social guidance. Mark is plagued by paranoia as to how others perceive him, and by doubts over whether his actions are normal. In spite of his thoughtful and sensible exterior and his tendency to act as the moral centre of his surroundings, he has frequent bouts of selfishness, schadenfreude and impulsive behaviour. He loathes many aspects of modern culture, such as drug use and openness of sexuality; he often simply endures activities that others around him enjoy, viewing them as "the price you pay to avoid loneliness". Despite this, he has a chronic fear of loneliness throughout the show, and continuously perseveres with doomed and irrationally motivated romantic relationships as a result.

Mark's political sympathies are arguably the most developed of any character in the show, and yet they retain some ambiguity. He appears to be politically rational, if socially the exact opposite. He is mildly Eurosceptic, but overall his views appear to be left-of-centre. What could be misconstrued as socially conservative views on his part (such as his disdain for drug use and free love) are more likely motivated by a hatred and fear of other people than a right-wing viewpoint. In the second series he says that "Tony Blair isn't such a bad thing", but in the fifth he claims "nobody wanted New Labour" and shows admiration for Paddy Ashdown of the Liberal Democrats. At one point Mark refers to "the miracle of consumer capitalism" as the backbone of society, albeit often with pessimistic acceptance rather than enthusiasm. He genuinely abhors bigotry and far-right politics, which in Series 2 causes him to lose one of the few true friends he had made onscreen aside from Jez. Mark often criticises those who believe in God, but has been seen praying in times of extreme panic. Although it is never stated in the show, his surname is of Irish origin.

When the series starts, Mark has already been a loan manager at a London branch of JLB (a Frankfurt-based loan and credit company) for around four years, at least judging from the timing given by Jez in Series 2. His time at JLB comes to a close when the branch closes down in the first episode of Series 6; later on, Mark works as a waiter at the Mexican restaurant Banditos, as a bathroom equipment salesman at Bath, Bathrooms, and Fittings, and finally again as a loan manager at the fictional Met City Bank with his former boss Alan Johnson. He is fired in the series finale, partly because of Jeremy's belated reaction to an abusive loan Mark had set up for him at the bank.

Mark's obsession with Sophie and his relationship with her (which is his first), is a major storyline of the first four series. She is seen almost exclusively through his eyes, showing her as merely kind-hearted and preventing the audience from understanding her real personality or motivations. By the third series, however, she is revealed to be narcissistic, boring, impulsive, and abrasive. These revelations coincide with Mark finally getting the chance to get together with her, but Mark is shown to be by this point increasingly apathetic towards her. Nonetheless, he perseveres neurotically with what becomes a passionless relationship bereft of mutual understanding. Mark appears completely unable to comprehend what type of man Sophie wants him to be. She takes no interest in his personal interests, such as history, fuelling him to attempt to lean into his masculinity (which, to her horror, leads him to briefly carry a large knife around). The two become increasingly frustrated and uninterested in one another, but Mark is in denial about what a healthy relationship looks like and refuses to accept that theirs is doomed. Mark's paranoia surrounding loneliness reaches fever pitch when he determines he must marry her or she will eventually leave him. While on a weekend trip with Sophie to Somerset, during which he plans to propose, Mark realises with Jeremy's help that he doesn't actually love her and should break up with her. However, she finds the planned engagement ring before he can tell her this and "accepts", apparently mostly out of a desire to have children. Mark feigns happiness out of fear of humiliation. The pair spend an agonising next few months preparing for a wedding neither truly want (especially Mark), with Mark and Jeremy coming up with increasingly outlandish schemes to get out of it that Mark could never actually succeed with.

Following Mark's and Sophie's disastrous wedding and separation immediately afterwards, he pursues a series of other women during series 5, wondering whether each could be "the one". After he and Sophie have sex following their breakup, she becomes pregnant and later gives birth to Mark's son.