I saw the hilarious Get Him to the Greek, a spin-off of the also very funny 2008 film Forgetting Sarah Marshall. Both feature Russell Brand as Aldous Snow an expired rock star. Jonah Hill is casted perfectly as the overweight, nervous and ambitious music producer Aaron. The film is a road movie where Aaron must get Aldous to LA for a live concert.  Aaron even end up in bed with his girlfriend and Aldous during a threesome ;-)

Also mentionable is Sean Combs as an over-the-top music exec.