Before it goes off the rails into strained sermonizing, this sorta-sequel to 2008’s delightful Forgetting Sarah Marshall gets in big laughs. Bad boy supreme Russell Brand is back as Aldous Snow, the Brit rocker whose addictions merely start with sex and drugs. Jonah Hill also returns, strangely not as Matthew the waiter but as Aaron the junior record exec. Aaron’s boss (a sidesplitting Sean Combs) charges him with getting Aldous from London to the Greek Theatre in L.A. for a comeback concert. Complications ensue. Don’t they always? The big miss here is Jason Segel, who wrote and starred in Sarah Marshall. Director Nicholas Stoller takes over the screenplay chores, letting the air out of Segel’s balloon. Making Aldous regret his wicked ways is a buzz-kill of major proportions.