Like pretty much anything that Melissa McCarthy does these days, your enjoyment of “Tammy” will depend entirely on how you feel about the actress as a performer. Those who can’t get enough of watching her play the same sloppy and obnoxious character over and over again will probably think that it’s the funniest comedy of the year. But for those who were already sick of her tedious, one-trick pony act after “Bridesmaids” launched the actress into superstardom, sitting through McCarthy’s latest movie is about as pleasant as a punch to the face. “Tammy” is so groan-inducingly dumb that it rivals some of Adam Sandler’s worst comedies, placing so much faith in its leading lady’s raucous, over-the-top antics that it doesn’t even consider it might not be funny.
McCarthy stars as the title character, a slovenly loser who wrecks her beat-up car, gets fired from her job at the local fast food joint, and discovers that her husband (Nat Faxon) has been cheating with their neighbor (Toni Collette), all within the same day. Desperate to get out of town for a while, she agrees to let her alcoholic grandmother, Pearl (Susan Sarandon) – who has the two things that Tammy needs most: a working car and some cash – tag along with her on a road trip to Niagara Falls. But when they end up driving the wrong way, the two women decide to make the most of the mishap in an attempt to patch up their troubled past.