Liam John Neeson, OBE (born 7 June 1952) is an Irish actor known for Schindler's List, Michael Collins, Star Wars Episode I: The Phantom Menace, Taken and the Chronicles of Narnia film series.
In "Prick Up Your Ears", Peter mentions kids being more lost than Liam Neeson would be playing an American cowboy. For Neeson, that would be casting against type. In this appearance, he is voiced by John Viener.
Liam provides his own voice in "Brian's a Bad Father" when Brian uses the example of Zooey Deschanel playing the daughter in the film Taken as thinking outside of the box. Liam is seen instructing the kidnappers to send him her head.
Tired of Peter's constant drunken bragging about being able to beat up Neeson in "Fighting Irish", they head to Connecticut where Neeson is filming a new movie. When Peter is arrested, Neeson bails him out so that they may be able to have their fight and Peter is completely cowed, promising to do his bidding to keep from getting beaten up. But after he tells his friends that he won their fight, they find out the truth when they catch him serving Neeson. Peter has enough of being belittled and fight, getting badly beaten in the process. However, the guys are still impressed that Peter carried through on fighting Neeson.