- Sophie's Parents- Mark meets Sophie's parents for the first time and brings Jeremy along. Jeremy manages to have sex with Sophie's mom, and Mark accidentally lets it slip to Sophie's dad that he doesn't want to marry Sophie. When Mark and Sophie are given her grandmother's old cottage as an early wedding present, Mark decides he wants to marry her after all, if only for the cottage.
- Conference- Jeremy tries to pimp out his girlfriend Big Suze to Mark's boss, Johnson, which results in her leaving Jeremy for Johnson and moving in with him. Johnson puts Mark in charge of a team, working on a difficult project called "Project Zeus" but Mark's bossy and erratic behavior causes most of his team members to quit.
- Gym- Mark joins a gym so he can spend less time with Sophie. Jeremy gets a job at the gym when he realizes Nancy is working there, but things go awry when the gym's top personal trainer, Matt, discovers Marks's secret about his lack of feelings for Sophie, and begins to develop feelings for Nancy, who Jeremy is trying to win back. The boys must team up to get Matt fired.
- Handyman- Mark goes to his high school reunion and sees his old crush, Sally Slater, there, but is upset to find out she has married his old high school bully Foz, who is still determined to torture him. Jeremy and the bully team up to make fun of Mark. Meanwhile, Jeremy has been given an all-too-good job for his favorite musician, Russell, a.k.a The Orgazoid, but things go awry when he realizes his job mostly involves sexual favors.
- Holiday- Mark and Jeremy go on a stag weekend to celebrate Mark's upcoming wedding, where they meet two sisters, Aurora and Lucy, and their dog Mummy. Jeremy accidentally kills the dog, which results in him and Mark burning the dog's body and Jeremy eating the dog's leg to prove that the animal remains are a barbeque, when he is confronted by Aurora. Meanwhile, Mark contemplates a job in India in order to get out of the wedding.
- Wedding- Mark wakes up on his wedding day, realizing he really doesn't want to get married and needs to find a way out of it as soon as possible. After attempting to marry a stranger, get hit by a car, and run away from the wedding, Mark eventually gets married, only to be dumped seconds after the wedding by a traumatized Sophie.
Series 4 revolves, as always, around Mark and Jeremy, but with special emphasis on Sophie as well. Other characters who make brief appearances are Johnson, Big Suze (both shown in the episode Conference, Nancy (shown in Gym and Handyman, and the members of Sophie's family, including her father Ian, who appears later in Series 5 and Series 6. Series 4 marks the last appearances of Nancy, Penny,and Jaime. Super Hans is shown in Series 4, but only in the episode Handyman, which is unusual since Super Hans is a regularly recurring character.
Series 4, specifically the episode Conference, marks the beginning of the relationship between Big Suze and Johnson, which goes on until the episode New Year's Eve in Series 7 when it is discovered that she and Johnson have broken up (although it is clear they are having difficulties in the Series 6 episode, The Affair, when Johnson and Big Suze are shown still living together, but not speaking.
Series 4 also marks the official end of the relationship between Mark and Sophie in the episode Wedding and the official end of the relationship between Big Suze and Jeremy which is constantly on again and off again.