Melissa McCarthy's passion project Tammy has a surprising sadness and sweetness to it, even if it doesn't quite amount to the sum of its parts. 

Tammy—co-written by McCarthy and her husband Ben Falcone, who also directs—stars McCarthy as the titular character, a woman who, after losing both her job (at a fast food restaurant) and her husband, goes on a road trip with her grandmother Pearl, played by Susan Sarandon in prosthetic ankles. Pearl is a wild child—or, rather, a wild granny—whose penchant for boozing and cruising for guys seems at first seems like a tired riff on the old people acting inappropriately trope. Pearl encourages Tammy to drink while driving and engages in a raucous hook up with Earl (Gary Cole), a man she meets at the bar, forcing Tammy to sleep outside their motel room while she gets it on.

But as the movie goes on, Pearl takes on a tragic bent. Pearl's alcoholism and ailments aren't written off as a gag. She and Tammy are comrades not just in hijinks but in their self-destructive nature. Their alliance brings out the worst in one another. At times, that worst is amusing. Tammy's decision to hold up a fast food restaurant to bail out Pearl from jail is even funnier than it is in the trailers, thanks to a scene-stealing performance from Sarah Baker. At times, it's just sad. A drunken Pearl takes the mic at a lesbian Fourth of July party (yeah, it makes sense in context) to brutally insult Tammy. 

Tammy is by no means a perfect movie. It's an odd mix of family drama and silly set pieces, and there are parts of the movie that simply don't add up. An obvious example: the minimal age differences between Tammy (Melissa McCarthy, 43), her mother (Allison Janney, 54), and her grandmother (Susan Sarandon, 67) is distracting no matter how much they try to age up Sarandon.

Perhaps most frustratingly, McCarthy's Tammy feels under-developed. McCarthy and Falcone sometimes make her unfathomably uneducated. At one point she reveals that she doesn't know who Mark Twain is. At another, she demonstrates a misunderstanding of the words "pattern" and "galaxy." The moments get laughs, but it's unclear what McCarthy and Falcone are actually saying about Tammy's intelligence. What's also unclear is how Tammy got to the low point at which she starts the movie, aside from her obvious predilection for mucking things up in her life. (The movie alludes to a placid suburban existence she once led with her now-cheating husband, played by Nat Faxon. Toni Collette, as the woman who he's cheating with, is underused.)

Still, McCarthy and Falcone deserve some praise. They've made a movie that, while uneven, wants to be more than just a showcase for McCarthy's prodigious talents as a physical comedian. It's a movie that also, refreshingly, showcases women. Though, yes, there is a love interest for Tammy—played by the sweet Mark Duplass—he is not part of Tammy's motivation. One of the movie's most charming performances comes from Kathy Bates as Pearl's lesbian cousin, who is the one to give Tammy the movie's obligatory "get your life together" talk at her Fourth of July party. (And, honestly, I would watch an entire movie of Bates setting fire to things and dancing.)

Tammy has its flaws, but it's ultimately a stranger, more rewarding experience than its advertising campaign implies.