Pineapple Express (15)

Or, Dude, Where's My Bong?

This stars the ubiquitous curly-topped Seth Rogen as a dishevelled legal clerk who witnesses a murder and goes on the run. The gimmick is that he has left behind a roach containing a wonder strain of weed known as Pineapple Express, whose rareness makes it traceable to his drug-dealer buddy (James Franco). The first half-hour floats by on a cloud of mildly funny lines ("couscous – the food so nice they named it twice"), but then slumps into a derivative action caper that's weirdly and unappealingly reminiscent of Eighties dross like Beverly Hills Cop.