Although Paddy only appears in The Hairy Ape in two scenes, he is an essential element of the play. Paddy is an old Irishman who likes to drink heavily, and he is known for his rendition of "Whiskey Johnny" and spouting philosophy and stories of the past when intoxicated. Although Paddy is quite a thinker, O'Neill describes Paddy's facial features as "extremely monkey—with the sad, patient pathos of that animal in his small eyes." Of the men on the ship Paddy could be considered the "extreme-monkey" because he has been doing labor jobs longer than most of the firemen—labor jobs fit for monkeys.

Paddy brings historical perspective to The Hairy Ape. His extensive monologue in Scene One details how shipping used to be aboard Clipper Ships. Without Paddy's presence the audience would not have as much perspective about the revolution brought about by machines. Paddy has experienced life on the sea that was free, where he was empowered and valued. Paddy, unlike many of the men, knows what it is like to not do slave labor.

Yank's continual references to Paddy as "dead" and "old" and not "belonging" with the other men aboard the Ocean Liner reveals Yank's own rejection of freedom. The acceptance and attachment to the modern-ship machine enslaves men like Yank. The need for belonging, without the knowledge of what else to belong to, is dangerous as exemplified by Yank's encounter with Mildred.

Paddy's characterization of Mildred in Scene Four demonstrates that he has real knowledge of the Bourgeois lifestyle. Paddy's description of Mildred's look and fainting spell in the stokehole defines Yank's own opinion of Mildred. Paddy's experiences let him have real opinions. While the development of one's opinion is definitely a process of age, it is also a benefit of freedom.