Office Christmas Party

“Office Christmas Party” starts out a little funny, a little sweet, and then slowly devolves into a dumb raunch-fest.

Don’t get me wrong: A good filthy comedy can be just the thing to break up the dull parade of PG-13 action flicks and kiddie fare (see the first “Hangover”). But when it’s not executed well it becomes like the loud, drunk guy at the party everyone wishes would leave (see, or rather don’t, the other “Hangover” flicks).

This is the rare movie where the fringe characters are more interesting than the stars. If you cut out everything with Jason Bateman, Jennifer Aniston, T.J. Miller and Olivia Munn, you’d have a discombobulated but very tight story of a bunch of office denizens caught up in the weirdest, wilding holiday party ever.

There’s the dweeby guy (Karan Soni) who’s been bragging to his fellow tech nerds about his hot nonexistent girlfriend, so he hires a prostitute to play her. Things go OK until she decides to freelance a little extra action from his buddies, and her she-pimp starts waving a pistol around.

Kate McKinnon of “Saturday Night Live” and “Ghostbusters” scores with another kooky character concoction, an uptight human resources manager named Mary who acts as the resident killjoy, but secretly has a freak flag in need of flying.

Then there’s the budding romance between single mom / office manager superstar Allison (Vanessa Bayer) and sweet-natured Fred (Randall Park), whose pet peeve is the underrepresentation of Asian men in adult films.

Fortune Feimster has a scene-stealing turn as a novice and overly exuberant Uber driver who hasn’t figured out what the appropriate level of chatter with the fares is yet. She keeps popping off one killer throwaway line after another, and I wished she would drop off Aniston and the movie could follow her the rest of the way.

But …

The setup is that the Chicago branch of a biggish tech firm is run by the ne’er-do-well son (Miller) of the dearly departed company founder. It’s a loose house and there’s plenty of goofing off, but they make money and realize growth — just not enough to please the hardcase CEO, played by Aniston, who happens to be his sister.

She’s got a lifetime of resentment built up over having to do all the work while golden boy slacked and got ahead, so she’s determined to cut costs to the bone — even ordering a 40% layoff, nixing bonuses and canceling the hallowed Christmas party.

Rich boy hatches a plan with his nice guy Number Two, Josh (Bateman), who really runs the office, to land a big contract with a major mover (Courtney B. Vance) and save everyone’s bacon. But, using the sort of logic that only works in movies, they’ve got to go ahead with the wildest office party ever to impress the crusty older dude.

Munn plays Tracey, the resident hacker whiz who has a plan to route Internet signals through anything electric, from street lamps to hot dog rotisserie machines. (Question: Once they flip it on and everyone’s got free wifi, how exactly do they make money?)

I think we all know where this is headed. There will be hookups and hilarious injuries, hard drugs will make an appearance, and some scary guys will threaten our heroes for about a minute-and-a-half. Just grab the plots from the “Hangover” movies and a smattering of ‘80s comedies like “Risky Business” and “Bachelor Party,” toss it in a blender and drink deep until you can’t take it anymore.