A cabal of comedians known for their slacker, stoner shtick playing themselves facing the apocalypse will either strike you as a great premise, full of self-deprecating potential, or a monstrously self-indulgent stool of postmodernism that’s sure to become the actors’ favourite movie featuring themselves but is less certain to feature on anyone else’s best of year list.

Well there’s good news and bad. This Is the End is neither one nor the other, falling into that lip-curling indeterminate territory in between. “You always play the same character in your movies” a paparazoid tells Seth Rogen in the film’s opening scene, the first of many winks at the audience, and what follows, though entertaining and high-spirited, never quite shakes the feeling stirred by that line, that in addition to the end, this is a gang of industry pals on a narcissist trip dressed to look like a self-aware deconstruction of their own middling celebrity.

Rogen’s boast that up to half the banter between him, Jonah Hill, James Franco, Jay Baruchel, Danny McBride and Craig Robinson is ad-libbed, will be no shock to an audience forced to listen to many a rambling and joke free exchange – an argument about cum, a tortured conversation about raping Emily Watson, an attempt to fairly divide up a Milky Way. In these moments, where the only brake on dick-waving attempts at in-scene oneupsmanship are the editor’s scissors, we might have asked co-writers Rogen and Evan Goldberg to write some jokes instead of letting their friends have full reign at the expense of the film’s wit. Instead this half of the film isn’t as funny as it thinks it is and consequently This Is the End often feels undercooked.

It’s always fun, there’s some excellent celebrity deaths (did Rhianna deserve to go to Hell? Umbrella’s not a bad single) and the half Rogen and Goldberg bothered to write has some decent lines, “I don’t want to die at James Franco’s house”, but it’s hard to shake the feeling that with a little more application and some varied personalities amongst the survivors, opening the door to jokes that didn’t rely so heavily on weed and junk sex, this could have been a wry little Hollywood satire, instead of a half-baked genre comedy with a postmodern twist.

The principles’ variations on their own personalities – Hill as a passive-aggressive hanger-on, McBride as a selfish, obnoxious arsehole, Michael Cera as a cokehead pervert – proves that all concerned had the right idea, but the egos involved ultimately blunt the movie’s edge. The end of the world turns out to be one prolonged exercise in mutual masturbation. It may end that way but wouldn’t it be nice to get in on the action instead of observing from a seat stained with coke and who knows what else?