Susan Sarandon and Melissa McCarthy in Tammy.

Melissa McCarthy takes most of the blame for Tammy, yet another bad comedy in which she plays an uninteresting mess of a human being.

She co-wrote the film and stars as the title character, a fast-food worker who wrecks her car, gets fired and finds out her husband (Nat Faxon) is having an affair—all in the same day. She winds up hitting the road with her alcohol-swilling, diabetic grandma (Susan Sarandon).

Despite the great cast, virtually nothing works as far as laughs are concerned. The script by McCarthy and husband Ben Falcone (Falcone also directs) tries to mine laughs out of grandma being a trashy party girl, and Tammy eating too much pie. It wastes the talents of everybody involved, including Gary Cole as a philandering barfly, and Mark Duplass as Tammy’s love interest.

When Tammy holds up her former burger-joint employer, it’s almost funny—but most of that scene is covered in the preview trailer.

McCarthy can be hilarious—her best film moment may be the outtake that shows during the This Is 40 credits—but she can also be tedious, as she is here and was in last year’s Identity Thief.

Her next film is St. Vincent, co-starring Bill Murray. Let’s hope that erases this one from our memories.

Tammy is playing at theaters across the valley.