If you watch the trailers for “Tammy” you'll see all the funny parts. That isn't because all the other jokes in the movie are bad. It's because the rest of the movie isn't really a comedy. Okay, this is an exaggeration, but “Tammy” is far more serious than the gangsta-rap dancin', jet skiing ads let on. Sure, we've come to expect a few dramatic patches and force-fed life lessons in vehicles for strong comedic voices. Hell, there's even a heart-to-heart in “Meatballs.”

But “Tammy,” the first feature film directed by Ben Falcone, starring Melissa McCarthy and co-written by both of them is basically a drama-in-disguise. Unfortunately, it's a formulaic and extremely uneven one, albeit with a number of sympathetic performances.

Things start out as you expect. McCarthy's titular lead is introduced as an adult-child in the “Step Brothers” mold. A barely functioning disaster area whose slovenly behavior nearly kills a deer on the way to her gig at a fast food joint. When she loses her job and her car is trashed you may think this will be some sort of set-up for Tammy to be the goofy new face of the downtrodden 99%. Turns out she lives in a well-to-do suburb, though she discovers her husband is cheating on her. That this cartoon doofus has a spouse in the first place is the first of many examples of “Tammy”'s core problem. Is this broad comedy or is this a real movie?

Tammy turns to her mother (Allison Janney) who lives two doors down, so, again, playing for silly laughs. After such a bad day Tammy decides to “run away” and Grandma (Susan Sarandon in old lady makeup) has the car and the cash to fund the trip. Crank the classic rock, they're on the road.

There are the typical roadhouse joints and motels and diners and if it weren't for the twinkle in Sarandon's eye or McCarthy's uncanny ability to squeeze a laugh from a throwaway remark you'd likely drop dead of boredom right there in the theater. There's a very funny sequence in which Tammy puts a bag over her head to knock over one of her old fast food restaurants – the added touch of Sharpie eyebrows are a source of genuine glee. However, the scene (and its unmotivated dance moves) takes a moment to find its groove, as it comes on the heels of a touching, somewhat depressing scene with Grandma.

Sarandon's character, you see, is actually an alcoholic, and as soon as Falcone decides he is making a Film With Themes, Tammy snaps out of her dingus routine and grows 100 IQ points. You'd think this would be infuriating, but here's the fascinating part. Once the film downshifts to its final third at a distant cousin's lakehouse, the Dr. Phil-esqu drama actually becomes. . .more compelling than the sub-par humor!

Blame this entirely on Sarandon's inability to phone this one in, I suppose. And also credit Kathy Bates (the cousin) and Sandra Oh (her wife.) It's enough to make you think that a fairly straight story about familial relationships with a few jokes tossed in might have been the way to go.

“Tammy” is still better than “Identity Thief,” but that movie is an all-time boondoggle. McCarthy was absolutely tremendous in “The Heat,” so she should still make big, silly comedies – still what “Tammy” is trying to be. She should just be cautious who she makes them with.