Top talent is wasted in this un-funny and disappointing vanity production from Melissa McCarthy and her husband, Ben Falcone.

They wrote it, or, more accurately, assembled it from pieces of other films, some better (“Thelma and Louise”), some even worse (McCarthy’s own “Identity Thief”). Falcone directed the film and appears as a fast food restaurant manager who fires the title character, played by McCarthy. Tammy is late to work because she ran into a deer and has been trying to resuscitate the stunned animal by blowing on it and making encouraging comments like, “Walk it off.” After she gets fired (contaminating the food in the kitchen by shaking her hair and rubbing saliva on it on the way out), she goes home to find her husband (Nat Faxon) entertaining a lady friend (Toni Collette). For the second time in ten minutes, she tries to make rejection and bad attitude funny.  For the second time, but not the last, she is unsuccessful.

She goes a few doors down the street to her parents’ house and tells her mother (Allison Janney) she is taking her grandmother’s car and getting out of town. Her grandmother, Pearl (Susan Sarandon), insists on coming along and provides a powerful inducement: more than $6000 in cash. And so, they’re off on the road in Pearl’s Caddy for a road trip comedy so derivative of every road trip comedy you’ve ever seen that it could be another in the apparently-assembled-by-robots “Scary Movie” franchise.  Will they visit a roadhouse and make bad decisions?  Yep.  Will there be arguments, revelations, and bonding?  Yep.  Encounters with old acquaintances and new friends?  And don’t forget the hilarity of being hospitalized and arrested and put in jail!

Like the odious “Identity Thief,” the movie wants to have it both ways.  We are supposed to laugh at McCarthy’s character for being loud, obnoxious, willfully dumb (she does not know who Mark Twain is, but pretends she does — funny, right?).  We are supposed to find it funny and endearing that she is at the same time both arrogant (she brags about her ability to seduce men) and painfully insecure and sensitive (she pleads with the girl she is robbing to be her friend).  Of course there has to be a makeover.  And then there’s the ever-popular old people having sex humor.  Yay!

The wisest decision McCarthy and Falcone made was in casting.  Sarandon is a joy, and of course efforts to make her seem old and infirm fail completely.  She is and will always be imperishably glorious.  Mark Duplass makes the most out of an underwritten role as a generic NICE GUY/LOVE INTEREST.  Kathy Bates and Sandra Oh are pure pleasure as a kind-hearted and generous couple, and Dan Aykroyd has a nice moment as Tammy’s understanding and supportive dad.  But the script’s sloppiness keeps getting in the way as characters’ major personality changes bear no relationship to anything beyond the needs of each individual scene.   Falcone clearly loves his wife and it is touching to see her and make her look beautiful without makeup (before the makeover, even with two-tone hair).  I can’t help thinking that the over-the-top antics were the trade-off to get financing for the film, and the quieter, more dramatic moments, some truly touching, were what interested them.  It is in those moments we get a glimpse of what McCarthy can do and it would be great to see her in a movie where she gets to take that journey instead of this one.

Parents should know that this film includes very strong and crude language, sexual references and situations, alcohol and drug abuse, comic peril and mayhem.

Family discussion: Is there a place you’ve always wanted to go? How did Bobby and Lenore make Tammy feel differently about herself? Why did she forgive her grandmother?

If you like this, try: “Bridesmaids” and “The Heat”