Liam is one of the McPoyles, a group of siblings including Ryan, Doyle and Margaret McPoyle, who are very odd and always looking for ways to make life miserable for the Paddy's Pub gang. The McPoyles are in incestuous relationships with one another and enjoy watching each other have sex with other people. Liam, like his brother Ryan, is particularly fond of wearing underwear and a bath robe, and his favorite drink is milk.