Sum 41 may have turned flippancy and potty jokes into brand tenets, but with 2004's Chuck—a politically aware collision of Top 40 punk and Iron Maiden-esque metal—the Canadian group reinvented itself, displaying a conscience to match its sizable chops. Since then, Sum 41 lost its chief metalhead (guitarist Dave Baksh) and turned over production to frontman Deryck Whibley (a.k.a. Mr. Avril Lavigne), but the result, rather than a regression into juvenilia, is the band's smartest and most mature-sounding album yet. Grown up in much the same manner as the still-snotty but newly politicized NOFX, Underclass Hero takes its subject matter as seriously as its chord progressions, from the Bush-bashing, Ramones-on-meth charge of "March Of The Dogs" to the lighters-aloft ballad "With Me" and the acoustic-driven Baksh farewell "So Long Goodbye." True, there's little to laugh at in Sum 41's current incarnation, but there's plenty here to make fans smile.