“Get Him to the Greek” is shamelessly funny. No seriously — it literally has no shame.

No body part is off limits, no sexual situation is too embarrassing to exploit and no ego is so precious it is spared from attack. It’s all exposed and hilarious in the most awkward, surprising ways.

Which makes the movie a reflection of its star, Russell Brand.

Brand plays Aldous Snow, a has-been rocker with major personal problems. He is estranged from his wife, pop singer Jackie Q (Rose Byrne). He rarely sees his son (Lino Facioli), who lives with Jackie. He’s a drug addict. His last release offended all of Africa and most of the rest of the world, too. And to rub it in, Jackie has emerged from his shadow to become a huge solo star.

On the other side of the pond, Pinnacle Records, run by Sergio Roma (Sean “P. Diddy” Combs) is in dire need of a hit. Pinnacle record executive and average shlub Aaron Green (Jonah Hill) thinks he can save the company by putting on an Aldous Snow comeback concert and re-releasing Snow’s back catalog.

Roma likes the idea and soon gives Green a simple mission: Green has 72 hours to fetch Snow from London and get him to the Greek Theatre in Los Angeles for the concert.

Once in the UK, Green gets caught up in Snow’s hedonistic lifestyle and struggles to maintain control. Green and Snow stumble across America, with Snow doing a “Today Show” appearance and making other ill-fated stops along the way.

What the movie does best is use real-life celebrities to lend itself credibility. Meredith Vieira, Kurt Loder, Lars Ulrich, Pink and many others show up in either cameos or supporting roles. After a while, it’s easy to forget that this is all a put-on.

And being surrounded by real pop culture figures makes Brand all the more believable as Aldous Snow.

Brand is like a rock star without the music career anyway. He certainly looks the part, he revels in shock value and he’s engaged to pop star Katy Perry. He published a book a couple of years ago titled, “My Booky Wooky: A Memoir of Sex, Drugs and Stand-up.”

So he isn’t playing the role of a rock legend as much as he’s playing around with his own persona.

He and the entire cast fit their roles perfectly and share obvious chemistry.

For all the crass, vulgar humor Hill spews in so many of his roles (“Superbad” and “Knocked Up” in particular), he can also be endearingly vulnerable and insecure.

The movie doesn’t quite make us believe that Snow would bond so quickly with a nobody like Green, but Brand and Hill are so hilarious together, who cares about character development?

Green and his fiancé Daphne (Elisabeth Moss) are adorable and have conversations that seem plucked straight out of real “relationship talks” we’ve all had.

But the biggest revelation of the movie is Byrne’s comedy chops. Her well-known roles (“Troy,” “28 Weeks Later,” the TV series “Damages”) have all been dramatic. Here, she plays a self-involved Lady Gaga parody who dresses in outrageous costumes and sings thinly veiled tributes to a sex act deemed illegal in some states.

Jackie Q is a spot-on send-up of the all-image and no substance poseurs currently topping real charts. She also is the ideal companion for Snow, and Brand and Byrne are by turns touching, titillating and just plain damned funny.

The third act unfortunately limps along to an anticlimactic finish, but these Judd Apatow-produced movies (“Funny People,” “Forgetting Sarah Marshall”) often do. They inevitably try to inject some heart, which pulls us away from the jokes.

Despite the weak ending, “Get Him to the Greek” is as much fun as you’re likely to have at the movies all summer.

Jeff Marker is a media studies professor at Gainesville State College.