Years ago, before the Xbox 360 launch, when the Live Arcade was just a pipe dream and Microsoft brains were envisioning what the pinnacle of XBLA could be, it was probably something like the idea of Castle Crashers. I say the "idea" of Castle Crashers, because anyone could imagine a multi-player 2D brawler with great co-op gameplay, but no one could imagine it like Dan Paladin and Tom Fulp, the minds behind the Behemoth.
Castle Crashers is an absolute blast. It features a perfect fusion of time-tested gameplay, an unbelievable amount of creative artistry, and enough additions to a classic formula to create a uniquely fun game that still triggers nostalgia.

The game plays much like the 2D side-scrolling brawlers you may have played in arcades: Teenage Mutant Ninja Turtles arcade games, the X-Men arcade game, or even Streets of Rage. You and up to three friends walk to the right, smash bad guys, and maybe take on a mini-boss on the way to the stage-ending big bad guy.
Simple? Yes, but the amazing hand-illustrated graphics and incredibly creative character designs (a giant cat, a mutant corn ear, and a hulking barbarian wildebeest...thing) make the game a joy to look at.
The combat system is good, too. As players level up, they gain access to new moves and combos automatically, and can assign skill points to attacks, defense, speed, and the very interesting magic powers. Each of the four knights available at the outset (many more characters are unlockable in multiple playthroughs) have different spells that really make a difference in character selection.