The reason the friendship works is that Russell Brand and Jonah Hill are good actors. Hill's character is required to be blotto half of the time, but there's the sense that he's desperately trying to do the right thing. Russell Brand is convincing as a rock star, imperious, self-destructive, smarter than he seems, calculating, measuring out wretched excess in survivable portions. When it comes time for him to sing, he does it convincingly, with songs that sound like real rock songs. I was reminded a little of Rod Stewart.