Sonny on a Cloudy Day
Though it isn't explained in the movie, Cloudy gets his nickname from his real counterpart, Sonny Grosso, who was known for his pessimism. Cloudy? Sonny? Sunny? Get it?
We kind of do.
The fictional Cloudy is less pessimistic than reasonable. Just like Charnier, Cloudy's character gets much of his depth from his reactions to the force-of-nature Popeye. Just check out his calm reaction to Popeye's raging racism:
POPEYE: You dumb Guinea. Never trust a n*****.
CLOUDY: He coulda been white.
POPEYE: Never trust anybody.
Cloudy doesn't say, "Whoa, buddy. Don't say that," or "You jerk! Shut your mouth!" He just says "Meh. He coulda been white." Sure, it was the 1970's, but Cloudy just seems to shrug whenever Popeye does anything even remotely weird. Here's another prime example of Cloudy basically saying, "Popeyes will be Popeyes:"
CLOUDY: What for, you wanna play hide the salami with his old lady?
In case you've forgotten, this is when they're trailing Sal. It's not all business with these two, but it is all Popeye, all the time.
In fact, we don't know much about Cloudy at all, except for the fact that he's Popeye's more grounded partner, and that he's loyal to him, maybe to a fault.
After all, what would Cloudy's life be like if he wasn't spending months on the cold streets of Manhattan and in tiny basement rubbish rooms, trying to gather evidence for a crime only his partner believes in? (Um. Maybe it would be better?)
The Buddy System
Popeye believes in himself, and Cloudy believes in Popeye. Cloudy fights the captain for investigative support, against the jabs of Mulderig, unlocks the man himself from his own handcuffs, always has his back. But a question worth asking is: why does Cloudy believe in Popeye?
The code of partners-in-arms can only go so far.