That's fine when you're strutting through the bars with your buds (Rob Brown, Jeremy Luke), bagging and bragging about it. Then Jon, whose pals call him "The Don," meets "a dime." Yeah, Barbara (Scarlett Johansson) is a "10" all right. But this Jersey girl has her eyes on the prize. Not Jon as he is, but Jon as he could be. She teases and tempts and grinds on him and has him enrolling in night school, rounding up his friends to meet her friends and trying to make his parents behave when they meet her.
"You don't think I could make you happy if I wanted to?" she purrs, and he's putty in her hands.
So Jon faces his dilemma -- giving up porn, or lying to Barbara, confessing his sins to the priest every week, doing his Hail Marys and "Lord's Prayer" recital during his reps at the gym and raging at the world from behind the wheel of his 1972 Chevelle.
Here's how tight this tale is: Gordon-Levitt wrote and directed this, and his spare script doesn't squander a single second at Jon's job (he's a bartender, apparently).
His friends' names have to be parsed from a single reference, and we never hear the name of his always-silent, always-texting sister (Brie Larson), a great, deadpan sight gag.
Tony Danza is riotously funny as the sports-obsessed, foul-mouthed rage-aholic dad who lets us see the tree that Jon fell from. Glenne Headly lands lots of laughs as his Catholic, grandchildren-obsessed mother.
Gordon-Levitt does sort of a Young Matt Dillon thing here -- all smirk and swagger and muscle shirts and goombah slang.
And Johansson, "Jersey Shore" twanging, gum-snapping temptation incarnate, gives the best performance of her career as a girl who just knows what she wants.
Watching her turn it off and on is to see a starlet in full command of her talent and her other assets.
Gordon-Levitt wasn't content to just create a world not far from the "Jersey Shore" and people it with funny characters. His brisk little comedy turns dark and deep in the third act. That's when the great Julianne Moore shows up as Esther, a funny / tragic and non-judgmental classmate of Jon's in night school.
Whatever Barbara promises to Jon if he cleans his act up, Esther is the one who might show this Don Juan that he's not in heaven, logging into porn 10 times a day. He's in hell.
With "Don Jon," Gordon-Levitt hasn't made a great movie. But he has made a fun one, short and sweet, with a third-act punch that is so to-the-point it'll take your breath away.