Aaron (Jonah Hill, left) and Aldous (Russell Brand) escape a Las Vegas party gone berserk in a scene from the music-biz comedy Get Him to the Greek. (Glen Wilson/Universal Pictures)

The new Judd Apatow-produced comedy Get Him to the Greek is a spinoff of his 2008 hit Forgetting Sarah Marshall, and it combines the best and worst things about that movie. The best, by far, was Russell Brand’s fey, sexy-silly British rock star Aldous Snow. The worst: Jonah Hill, the least funny of Apatow’s funny people, who appeared as a fawning waiter who tried to get Snow to listen to a demo CD.

After starting off by mocking the faux-sincerity of shallow rock stars, director Nicholas Stoller reverts to the faux-sincerity of a shallow comedy-drama.

Apatow and director Nicholas Stoller must have seen some comic chemistry between the two actors that the rest of us missed. In Get Him to the Greek, they've brought back Brand's Snow character and teamed him with Hill, now playing a junior record company exec named Aaron Green, who is charged with getting the wayward rocker to a concert at L.A.’s Greek Theatre.

The sympathetic role gives us ample opportunity to decide if Hill is better than we’ve hitherto suspected. The verdict, two hours later, is no – but you do have to give the guy credit for trying. In the course of this semi-funny music-biz spoof, his nebbishy Green is the butt of vomit jokes, dildo jokes and, yes, butt jokes, too. At one point, the poor sap has to play reluctant drug mule to the less-than-pure Snow, which involves concealing a rubber sachet of heroin in a certain orifice...

Hold on a minute, you say. Wasn’t Snow celebrating seven drug-free years in Sarah Marshall? He was, indeed, but that was before a pair of disasters: his relationship with trashy model-cum-pop singer Jackie Q (Rose Byrne) went belly-up and his single African Child plummeted down the charts. We see the video for the song in a hilarious opening scene – imagine a bleeding heart Bob Geldof ballad as performed with the bare-chested sleaziness of Devendra Banhart. “NME called it the greatest offence to African culture since the Rodney King beatings,” Snow says in a moment of sulky candour. After that, he hit the bottle and the needle.

In the U.S., however, Snow still has a die-hard fan in Aaron Green. The eager exec manages to convince his combustible boss, Pinnacle Records CEO Sergio Roma (Sean Combs), that the fallen rock god deserves a comeback concert. There’s just one catch: Aaron has to fly to London and escort his idol back to L.A. within 72 hours.

Predictably enough, Snow won’t come quietly. A trip to Heathrow airport sidetracks into an all-night party, in which Aaron gets sucked into a vortex of Bushmills, martinis, absinthe and sex-in-the-loo (an act, not a drink). When the two finally touch down in New York for a live appearance on the Today Show, Aaron makes a heroic if foolhardy bid to deliver Snow unsullied to the studio by guzzling all of the star’s available whisky and bogarting his king-sized joint. As for the result of his efforts — let’s just say it involves more vomit, which is something of a leitmotif in this movie.

The New York segment pays homage to writer-director Stoller’s most obvious inspiration, the 1982 comedy My Favourite Year. In that charming period piece, Peter O’Toole starred as a boozing British matinee idol and Mark Linn-Baker was the adoring New York Jewish kid who had to keep him sober for a guest spot on a live 1950s TV show. The film's story was slight and a tad corny, but it looks like a work of genius next to the by-the-book screenplay for this one.

Rose Byrne co-stars as model-cum-pop star Jackie Q in Get Him to the Greek. (Glen Wilson/Universal Pictures)

After successfully mocking the faux-sincerity of shallow rock stars at the start of the movie, Stoller reverts to the faux-sincerity of a shallow comedy-drama. Turns out that — surprise! — Get Him to the Greek is really a relationship movie, like most of the Apatow flicks. Aaron has to work through his imperiled relationship with long-time girlfriend Daphne (Mad Men’s Elisabeth Moss), a frazzled medical intern who wants them to move to Seattle where she has a job offer. Snow, meanwhile, has to work through his relationship with his estranged father, a Las Vegas sideman (Colm Meaney), as well as his lingering feelings for Jackie Q. All this serious stuff is a drag, and feels as superficial as the whimsical rider in a rock star’s contract.

The picture is much better when it sticks to being a satire of the music industry. That’s when comedian Brand is at his most inspired. His band may be called Infant Sorrow (a bookish nod to William Blake), but the decadent Aldous Snow is a wicked parody of geezer rock. Looking like the bastard child of Keith Moon and Jimmy Page, he prances about the stage with the prissiness of Mick Jagger, flashing a pair of wild-man eyes that could outstare Iggy Pop's. His Today Show number, The Clap, even sounds like a send-up of the Stones at their dirtiest. (Rock vet Lyle Workman provided the film’s witty music.) Brand also brings to the character his own double-edged comedic persona – part crude, part genteel, with an irresistible blend of devilry and disarming innocence.

He is perfectly complemented by Byrne. Free from the fetters of her dramatic role in the cable series Damages, the actress is deliciously flaky as Jackie Q. Imagine Elizabeth Hurley with the skanky sensibilities of Courtney Love. Combs also has a ball as over-the-top Sergio, not so much chewing the scenery as swallowing it whole. And Meaney is cheerfully acidulous as Snow’s grizzled musician dad. Then there’s the surfeit of celeb cameos by everyone from Metallica drummer Lars Ulrich to Christina Aguilera and Pink.

Toward the end, I began to wish there was one more star on the roster. I started to imagine what it would be like if that pudgy, unshaven little man paired with Brand wasn’t Jonah Hill, but Ricky Gervais. After all, Gervais could use a decent feature-film vehicle, and Brand definitely needs a better comedy partner.

Get Him to the Greek opens June 4.

Martin Morrow writes about the arts for CBC News.