You know a Porthos, even if you've never read The Three Musketeers. A Porthos (much like the Porthos) is loud, obnoxious, and likes to talk (loudly and obnoxiously) about how awesome he is. He's that guy who brags about high scores, number of buffalo wings eaten, and the number of girls he could totally date if only he wanted to. He also is—surprise!—a total sweetie-pie. Beneath that exoskeleton of I'm-So-Cool is a soft, cuddly guy.
When we first meet Porthos he’s dressed to kill: he’s wearing a baldric (basically a sword-belt) made of gold. We soon discover, however, that this baldric is a one-sided affair. Ye olde baldric doesn't extend around Porthos’s back. This introduction to the loud, talkative, and braggart Porthos gives us a solid understanding of his character.
He likes to be ostentatious and is obsessed with status. He brags about all of his lady conquests. In particular he is most proud of a certain duchess who, we discover, is really just the old and ugly wife of a wealthy lawyer. Still, despite his propensity to overstate his awesomeness, Porthos is a deeply loyal friend and courageous fighter. But ultimately, all he really wants is to be crazy-rich:
"Yes," said he, "yes, that would flatter me very much; but I should not have time enough to enjoy the distinction. During our expedition to Béthune the husband of my duchess died; so, my dear, the coffer of the defunct holding out its arms to me, I shall marry the widow. Look here! I was trying on my wedding suit. Keep the lieutenancy, my dear, keep it." (67.118 – 67.120)
Sure, he's shallow. Sure, he's marrying a widow for her money (or maybe he actually truly loves her? Nah.). But when the going gets rough, so does Porthos... he'll take a bullet for his bros, and he lets everyone know it.