We loved her in Bridesmaids, but now Melissa McCarthy is taking center stage as Tammy, a down on her luck former fast food employee, who turns fugitive and hits the road with her grandmother. Tammy’s grandmother happens to played by Susan Sarandon, while Kathy Bates and Alison Janney also co-star. But despite the impressive cast and McCarthy’s charm, the critics just don’t seem to be warming to Tammy ahead of the big 4th of July weekend.

Melissa McCarthy takes center stage in Tammy

Written by McCarthy and her husband Ben Falcone, who also takes the director’s chair, Tammy was supposedly meant to be the perfect showcase for the comedienne’s talents. Since her breakout Bridesmaids role, McCarthy’s screen presences has continued to grow. She’s taken co-leading roles with Sandra Bullock and Jason Bateman in The Heat and Identity Theft, but Tammy is the first time she’s been given a solo top billing.

But sadly Time’s Richard Corliss sees the movie as nothing more than a “vanity project” for McCarthy, as he points out the film’s various plot holes and problems. These problems include the fact that Susan Sarandon is in no way believable as McCarthy’s grandmother. Corliss writes, “the genetic and chronological anomaly goes unremarked, and we’re left with the most implausible three-generation movie trio since the 1988 crime comedy The Family Business.”

More: Susan Sarandon's Glow Had To Be Dimmed For Grandma Role In Tammy

Writing for Variety, Justin Chang has a similar problem getting to grips with Tammy’s family. “The (mis)casting decisions are so surreal as to seem almost deliberate at times,” he writes. “When Allison Janney pops up early on as Tammy’s mother (Janney is 11 years older than McCarthy and 13 years younger than Sarandon), the sheer randomness of it — and the sheer number of bizarre wigs being worn at any given time — pulls you out of the picture, never to fully return.”

TammyMelissa McCarthy in 'Tammy'

Watch the trailer for Tammy here

But it’s not all doom and gloom for Tammy, despite the plot problems and the movie’s predictably, it has managed to convince some critics that McCarthy has the makings of a star, even if she is in need of a better script. “Tammy may not a comedy masterpiece, but McCarthy has comedy star quality,” writes Peter Bradshaw in The Guardian. While The New York Time’s Manohla Dargis, notes that McCarthy’s weight is all too often played for laughs, she describes the comedienne as, “beautiful, funny, wildly popular.” Adding that she also posses, “terrific timing, movie star presence and oodles of charm.”

More: Melissa McCarthy And Husband Ben Falcone Share Intimate Moment On GQ's Front Cover

One critic who was bowled over by Tammy was Forbes’ Mark Hughes, who describes the movie as ‘a winner’. “Tammy is Melissa McCarthy at her best, frank and raw but in a much more honest way than we’ve seen before,” he writes. Adding that it, “takes a version of McCarthy’s usual harsh, crass comedic character and reveals her humanity and, ultimately, her dignity.”

Tammy was written by McCarthy and her husband Ben Falcone

With only a 19% rating on Rotten Tomatoes, Tammy isn't the best debut McCarthy could have hoped for. Still if you enjoyed Identity Theft and The Heat, sitting through 90minutes of Tammy shouldn’t seem like too much of a chore. Just remember you might have to leave all logic at the door. especially when McCarthy introduces Susan Sarandon as her grandmother.