InThe Hairy Ape, Paddy is described as follows:
...an old, wizened Irishman who is dozing, very drunk, on the benches forward. His face is extremely monkey-like with all the sad, patient pathos of that animal in his small eyes.
Paddy has been a worker on ships for a long time, and is now too old to shovel coal with the other shovelers; he performs menial labor around the ship and provides commentary from the perspective of someone who has worked on ships with better technology. His age and the overarching theme of "Man as a Hairy Ape" are physically embodied in his face, which is wrinkled and drooping, "monkey-like." However, unlike the other workers and Yank especially, Paddy has perspective beyond the ship and its labor, and understands the upper-class lifestyle; he is the one who says:
...she shrivelled away with her hands over her eyes to shut out the sight of him! Sure, 'twas as if she'd seen a great hairy ape escaped from the Zoo!
(Quotes: O'Neill, The Hairy Ape, eoneill.com)
Paddy's understanding of the difference between the working-class proletariat and the upper-class bourgeoisie is the catalyst for Yank's undoing; in a way, his description as "monkey-like" is entirely satirical, since he is far more civilized than Yank, the "hairy ape." Therefore, his physical resemblance to a monkey is less important than his mind and memories; he sees beyond the simple class distinctions to the inner self, and knows that Yank can never fit in with the upper-class.