Rapping with cartoon characters was artistic suicide until Gorillaz dropped a bomb in 2001 with a platinum album and what turned out to be a surprisingly long shelf life. Next out of the box is Danger Doom, the stunning and welcome collaboration of two of hip-hop's most innovative artists, both of whom already have close ties to the world of animation — Danger Mouse not only named himself after a cartoon but is also a part-time Gorillaz beatmaker, and the rapper MF Doom has imagined himself variously as a comic-book character and fire-breathing monster-movie hero (not to mention, he's rarely photographed without wearing an iron mask that makes him look like an early version of the Marvel supervillain Doctor Doom). Their partners for The Mouse and the Mask are the characters of Cartoon Network's Adult Swim programming block, a cast whose creators share with Danger Mouse and MF Doom the same influences (obscure '70s superheroes, some making a resurgence on Adult Swim) and motivations (a parade of surrealist fantasies intersecting with real life, like the crusading happy meal that airs on Cartoon Network as Aqua Teen Hunger Force). Granted, none of these cartoon characters are rappers, and they're wisely given only backgrounds, transitions, or samples (all of them hilarious). No, it's the experts who handle nearly all of this record, and they're at the top of their game. Doom's dense flow and ciphered allusions have much in common with Adult Swim; both presuppose a large body of cultural knowledge to appreciate what's going on and both rely on a series of bankable eccentricities presented at light speed with high artistry and innumerable subtleties for later parsing by fans. Danger Mouse's productions have the same punch and catchy flair as on Gorillaz's Demon Days, but they're even more impressive here with the absence of Damon Albarn's interference and need to court a pop audience. He calls on the same type of rollerskating pianos, brassy fanfares, flutes, vibraphones, and cavernous drum loops that anyone of a certain age will recall from Fat Albert or Electric Company. It all adds up to the best album of the year in the hip-hop underground, and perhaps the best with any degree of popularity.