While some viewers of The Night Of grew invested in characters like Nasir Khan (did he kill Andrea or not?!) and John Stone (will his eczema ever go away?!), others were more attached to an unexpected star — the cat. He became such an onscreen force that viewers even began to theorize that the cat was the killer. He wasn't, of course, but he's still a vital part of the series.
The cat is first seen in the pilot, getting in the way of Naz and Andrea's spontaneous tryst due to Naz's allergies. Andrea lets the cat out of her home through a gated entrance, and because of the unfortunate events that send the story into motion, he's left outside for a bit. Soon enough, Stone examines the crime scene and lets the cat back in. While the gate becomes an important part of the trial as a potential break-in point, it's also worth noting that Stone takes pity on the now ownerless cat and takes him to a local animal shelter. Despite initially seeming indifferent, Stone actually calls to check up on him. When he learns that he hasn't yet been adopted, he takes the cat in to prevent him from a grim fate.
You may be thinking, "OK, but are we really watching a love story between a man and his new cat?" Well, yes, but it's also more meaningful than that when you consider that the cat mirrors Naz in many ways. For instance:
In the finale, Stone returns the cat to the shelter. This comes immediately after Naz's lawyer Chandra calls him to the stand at his trial, a move which has Stone convinced that he'll be convicted. The cat's fate is uncertain until the end of the episode; the last few seconds show him inside Stone's place. And he's actually let loose rather than behind a door! (Cue the internet's collective sigh of relief.) Similarly, Naz is released from prison, though his story's left quite a bit more ambiguous. Prison has changed him to the point where he doesn't immediately bounce back to his old life, so it's hard to say if he'll ultimately experience the safety the cat receives.
Two things are clear though: the cat is way more important than he appears, and he may just be the show's breakout star.