Vince Vaughn, like so many other modern comedic actors (Will Ferrell, for instance), plays one character. When the material is good and the surrounding cast on point, and he's actually trying, Vaughn can be extremely funny. He's almost involuntarily gilb, sort of Robert Downey Jr.'s chubbier, taller, less charming, less suave cousin, with a kind of teddy bear vulnerability and juvenile self-destructiveness. Old School, Dodgeball, The Break-Up, even Fred Claus are worthwhile in no small part because Vaughn plays this aging slacker version of his younger Swingers self, the middle-aged man in slouching refusal to grow up, though his smirk is dissatisfied, his smugness threadbare. Vaughn's characters are often unlikable and yet lovable, each one a man-child stumbling toward adulthood. (Note: when Vaughn mails this persona in, it is unwatchable. I give you Delivery Man).
Wedding Crashers is perhaps Vaughn's opus in this mode (with apologies to Dodgeball). The writing is fantastic, the cast perfect, and Vaughn's Jeremy Gray is the most strangely centered of all his characters, the most self-actualized even as he might be the most loathsome. This is, after all, a dude who is a semi-professional predator, a troller of wedding receptions for the emotional flotsam and jetsam of female guests. This is unapologetically sexist and exploitative and hilarious. Jeremy and his Wilsonian sidekick John are dancing along a tightrope, and that perpetual risk is surely part of what drives them (along with the cheap and insubstantial sex with a parade of C-cup conquests, of course). They play by their numbered rules and they play like champions, but it's axiomatic that a fall is coming for them both. The revenge of the distaff comes in the form of Isla Fisher and Rachel McAdams, the latter of which engages in a long-form romcom courtship with John, and the former of which outplays Jeremy at his own game.
That Jeremy is so simply seduced by his own schtick and embraces it so fully is part of what makes this Vaughn's finest animal. He is shallow and seeks his own shallowness, and in finding it, is enriched immensely, unlocking the other 90 percent of his heart. More than just the tip, just for a minute, just to see how it feels.