Liam McPoyle is a member of the McPoyle family.
Throughout the series, it is implied that Liam is in an incestuous relationship with his brother, Ryan and sister, Margaret. It is also demonstrated that he likes to watch his siblings have sex with other people. Like his siblings, Liam likes to crank the heat so he is constantly sweaty. His attire of choice is underwear and a bathrobe. His favorite drink is milk. The McPoyles have a complicated relationship with the gang, usually as enemies, but are occasionally shown to be more friendly and socializing at the bar ("Charlie Got Molested", "Who Got Dee Pregnant?").
Liam is notable for sudden outbursts of tone and volume in his diction. He typically speaks with a lazy, laconic mumble, but is known for his violently impulsive comments about issues in which he is passionate and angry.
Liam seems to favor "fist bumps" as a sign of solidarity or friendship, but only offers a limp-wristed fist to his counter-parts (usually Charlie), followed by the insistence that they "bump it".
Liam is clearly dominating the relationship with Ryan, telling im what to do ("The Gang Gets Held Hostage"), admonishing him ("Charlie Got Molested"). When Ryan wants to stop him from marrying Maureen, he even gets Ryan to apologize to him instead.
Liam and Ryan accused Coach Murray of sexually molesting them when they were in elementary school. Upon hearing this news, Charlie grew concerned and visited the McPoyle's apartment. There, he told them he knew they were faking, but they threatened to turn him in as the ring leader if he didn't go along. They watching his mother hold an intervention for him, but Charlie later ratted them out to the police, who had them arrested. ("Charlie Got Molested")
Liam, along with a caravan full of McPoyles, comes across the gang again at the Eagles tryout which ends with Frank accidentally shooting Doyle in his leg.("The Gang Gets Invincible") As revenge, Liam, Ryan, and Margaret take the gang hostage in Paddy's, forcing them to destroy the bar. However, it is revealed that the gang was never in any danger as the McPoyles merely used rubber guns ("The Gang Gets Held Hostage").
Liam had eventually a falling out with Ryan, telling Charlie Ryan was dead to him and planning to marry Maureen Ponderosa. Ryan wanted to stop the wedding since Liam was tainting their bloodline which "has been pure and clean for a thousand years". Ryan sneaked into the wedding ceremony, but Liam convinced him he wasn't tainting their bloodline, but others', proclaiming the McPoyles would take over the world. However, the wedding soon descended into chaos and violence due to Bill Ponderosa spiking the milk with bath salts. Liam and Maureen do not marry, with Maureen beeing back in love with Dennis Reynolds ("The Maureen Ponderosa Wedding Massacre"). During the chaos, Pappy McPoyle's bird Royal picked out one of Liam's eyes. Liam blamed Bill for the loss of his eye, suing him, claiming Ryan stabbed him in the eye under the influence of the spiked milk, but the case was, after a chaotic trial which ended with Royal picking out the Lawyer's eye, thrown out of court. ("McPoyle vs. Ponderosa: The Trial of the Century")
He and Ryan also bought a video rental store, investing "in an emerging market." ("The Gang Squashes Their Beefs")
- Season One: "Charlie Got Molested"
- Season Two: "Charlie Goes America All Over Everybody's Ass"
- Season Three: "The Gang Gets Invincible", "The Gang Gets Held Hostage"
- Season Six: "Who Got Dee Pregnant?"
- Season Eight: "The Maureen Ponderosa Wedding Massacre"
- Season Nine: "The Gang Squashes Their Beefs"
- It’s Always Sunny: Gang Goes Mobile
- Liam is a left-hander. ("The Maureen Ponderosa Wedding Massacre")