Tammy gets fired from her job at a fast-food restaurant. Just before that, her old Toyota Corolla breaks down on a backroads highway. After she gets fired, she finds her husband has prepared a delicious meal for the next door neighbor – a lady friend. He's having an affair and the money they had in the house fun jar atop the cabinets has all but disappeared. For Tammy, can life get any worse?

After she packs her clothes and heads to her mother's house two doors down, Tammy realizes she needs to get outta town. And so does her Granny. Grandma, who lives at mom's house, has a shine for whiskey and oxycontin. The pair decides to ditch their sorry lives and take to the road.

Does any of this sound funny, or wait, original to you? Since Melissa McCarthy's television and movie success ("Bridesmaids," "The Heat," "Identity Thief") she's become the female comedic darling at the box office. But with "Tammy," McCarthy's star may be on the verge of burning out.

You have to hand it to her, though. She does have star power. And not only can McCarthy get fans in the seats, but it appears that she can get anyone to star in her movies, too. Susan Sarandon (who is only 24 years older than McCarthy, by the way) dons a bad gray wig to play granny. Her talent is wasted as Pearl as she ends up being nothing but McCarthy's sidekick. She's also forced to tell bad jokes, have "second base" sex in the back of a car with Gary Cole, and hold up a fast-food restaurant in a riff to the hit "Thelma and Louise." (Had the filmmakers used Sarandon and created something smart and sassy with the "Louise" reference that could have earned "Tammy" a few comic points. But, the writers blow this opportunity.)

McCarthy co-wrote the script with her husband, Ben Falcone, who also directs. Will Ferrell's name is listed as a producer. There are other A-listers in the film including Kathy Bates as Pearl's laid-back lesbian cousin, Lenore. Sandra Oh plays Lenore's younger girlfriend Susanne. Alison Janney shows up as Tammy's mom and Dan Aykroyd is her dad. Toni Collette plays the neighbor who is involved with Tammy's hubby. And Mark Duplass is Tammy's love interest.

McCarthy and Falcone ultimately need this team of actors to pull off their "been there, done that" script. Once again, McCarthy plays the sad sack with the salty tongue. The comedy never rises to any occasion and, in an effort to try to show McCarthy's depth in her first starring role, a sappy life lesson is plopped in (Bates has the task of delivering the fire and brimstone speech). Different shades of Tammy never surface. In fact, the movie is pretty much Tammy one note.

Falcone and McCarthy really could've made something good here, using McCarthy's gift of comic timing and the great cast they collection. Instead they resort to the typical road trip movie. How many times can one take off from a one-horse town, see the American landscape, and end up in a utopia of self discovery? Darn, if only real life was that easy. Perhaps I need a granny with a blue Cadillac and a wad of cash who wants to see Niagara Falls.

There are a few (and I mean a few) smart jokes (Tammy thinks Neil Armstrong is the cyclist who won the Tour de France) and granny has an interesting tale of sleeping with one of the Allman brothers. But like Tammy's watercraft crash, one of the many pratfalls in the film, this Fourth of July movie is a wash out.