Stubb is the boorish uncle that makes says mean things at the Thanksgiving table and then says "Can't you take a joke?" But he's also the guy who diffuses tension you can cut with a knife with that same arsenal of hilarity, so you can't be mad at him all the time.
Stubb, the second mate on board the Pequod, is a jolly man from Cape Cod who likes to laugh in the face of fear and light his pipe for a calm smoke in the middle of a whale hunt.
Stubb reacts to basically any situation in Moby-Dick you can name—hunting a whale, butchering a whale, agreeing to go on a crazy revenge quest, whatever—by laughing and saying that everything is predestined anyway, so he might as well take it all in stride and have a good guffaw. Ishmael tells us that Stubb "presided over his whale-boat as if the most deadly encounter were but a dinner, and his crew all invited guests" (27.1).
Of course, as you might have guessed, this tendency to laugh at fate and tell it to pull his finger are all an elaborate way to cover up that, deep down, Stubb is a coward desperately afraid of what’s going to happen to him. (And, um, he should be.)