Aldous Snow is living the rock ’n’ roll nightmare, stuck on the downside of a career sabotaged by canceled gigs, bubble-brained vanity projects and addiction. He’s blazing a path to the front page of the tabloids, his days and nights a blur of sex and drugs, and it’s not just his music that’s suffering.

Enter Aaron Green, the junior record exec and diehard fan determined to resurrect Snow’s career – and jumpstart his own – by convincing the world’s most decadent rocker to revisit the stage that made him a star, at the Greek Theatre in Los Angeles. Snow, now a laughable self-parody, embraces the plan, but following through is last on his list of priorities.

We’ve seen Snow as a supporting character before, spewing vacant New Age philosophy and liberally spreading his seed in Forgetting Sarah Marshall (2008), but Get Him to the Greek, in which British comedian Russell Brand reprises the role, gives him a leading man’s depth. His narcissism and simple-minded politics (“War is bad!”) are played for laughs, but behind the airhead persona lurks a subtle, redeeming wit.

One of Brand’s gifts is his wide-eyed, childlike charm; as Snow, he’s the kind of guy you just can’t stay mad at. Aaron (Jonah Hill), his sometime straight man, learns this the hard way. Hill played a similar role in Sarah Marshall, as a gushing fan who worships the oblivious rock god, but this time he’s not so hopelessly fawning; occasionally he zings as good as he gets.

Fueling Aaron’s fire to get to the Greek is Sergio, a music mogul played by Sean “P. Diddy” Combs, whose deranged, profanity-laced tirades rouse Aaron from his initial reticence to rein in his hard-partying hero. As he did in Jon Favreau’s buddy comedy Made (2001), Combs pokes fun at his own “gangsta” image, and though he seems to know only one mode – overdrive – he has a naturally likable on-screen presence.

The same is true of Brand, a gifted physical comedian who emerges in Greek as an actor with range. He shares an appealing chemistry with Hill, a veteran of Judd Apatow-produced comedies like Superbad (2007) and Sarah Marshall, and plays the role of an ego-driven junkie quite nicely. But the key to his performance, and the movie, is the vulnerability masked by his drinking and drugging.

Snow might be an arrogant jerk, but he’s a loyal one, and as he stumbles into self-awareness, after memorable misadventures in New York and Las Vegas, he becomes surprisingly human. The friendship he forges with Aaron, over drinks and one powerfully toxic joint known as a “Jeffrey,” is genuine.

Apatow, who produced, and Nicholas Stoller, who directed Sarah Marshall, are no strangers to this territory: Their deft mix of raunchy humor and heartfelt male bonding is familiar, but here, in a Greek odyssey even Homer might have appreciated if he'd been a little bit stoned, it remains immensely satisfying.