Disappointing sequels are common, but “The Hangover Part III” is bad in such a way that it makes the original film less likable.

The premise that made “The Hangover” so successful is gone. Our characters spend this film mostly sober, chasing Ken Jeong’s diminutive mobster Leslie Chow after being threatened by a rotund mobster named Marshall, played by John Goodman. The Wolf Pack still consists of Phil, Stu and Alan, while Doug is held captive by Goodman’s character.

The result of this new plot, which is taken much more seriously and lacks an actual Hangover, is a movie that is too dark, too serious and not very funny.

From the beginning, viewers get a closer look at Zach Galifianakis’ Alan as a character who is no longer the quirky screwball sidekick, but a bearded man-child with serious mental issues. I felt sorry for him and found it more depressing than funny.

There is also way more Leslie Chow than any movie needs. In this film he moves from an amusing supporting character to the primary villain. Like Alan, he goes from goofy comic relief to an actual sociopath who provides irritating whines and mediocre gay jokes.

It’s a darker movie, too. A giraffe, pair of dogs, a few people and a cocaine-addicted rooster all meet their demise in manners that aren’t even funny in a black comedy approach.

The mobster Marshall is one of John Goodman’s least inspired performances, though he does have a few lines that reference his legendary performance in “The Big Lebowski.” But what does it say about a movie when the best line is a reference to another movie?

“The Hangover Part III” is a misguided attempt to change the formula of a series where the formula was what made it good to begin with. It’s dark. It’s sobering. It’s not very funny.