James Morosini’s “I Love My Dad” grabs the eternal adage of “write what you know” and sprints towards the edge of a cliff. The story is true: Morosini’s father pretended to be someone else online in order to check in and be close with the son who had blocked him on social media. It’s such a bizarre concept, such a painfully sad move to be close to someone, that you have to laugh. “I Love My Dad” lets the viewer do that over and over, creating a roller coaster ride of one desperate and awful idea after another, one that’s bound to crash and burn albeit with confident style. Writer/director Morosini plays himself in the situation, as a young man named Franklin who has just left rehab after living through a suicide attempt. He’s awkward and a bit anti-social, and he’s estranged from his father Chuck after years of serious let-downs. Not long after Franklin gets home, he receives a friend request from a woman named Becca who lives in Maine; he accepts the request with some hesitation, as she has no other online friends. But Becca seems real enough in how she talks, and the attention and care she provides Franklin is flattering, comforting. He quickly develops an online crush; he wants to travel from Massachusetts to Maine and meet her. But on the other side of the screen, Becca is actually Chuck, and “Becca”’s pictures have been stolen from a kind diner server named Becca (Claudia Sulewski) that once told a teary Chuck that “talking to people’s a good start.” Patton Oswalt plays the version of Morosini’s father with great heart, as he has for other complicated loners (“Young Adult,” “Big Fan”) and it’s one of the comedian’s very best performances in a film. While the movie never excuses Chuck’s horrific sense of boundaries, or of being a bad dad for so long, Oswalt’s performance nudges us that maybe this is indeed the time when Chuck is ready to be a more present father, which makes catfishing his son all the more tragic. Without playing the grossness or darkness too obviously, Oswalt shows the desperation within Chuck to be back in his son’s life; he also is able to (mostly) sell the film’s digs at Chuck’s clumsy understanding of modern technology and chat lingo. With Oswalt’s sensitivity as an actor, a character who proves to be a liar, avoidant, invasive, and so very manipulative still becomes watchable. Maybe he’s even endearing. There’s a sneaky savviness to this story that wants to see how far it can take this scenario, and it comes in depicting the conversations. The movie visualizes the intimacy of a fluttery text session as if they were dates happening in-person, as daydreams coming true during a long-distance relationship. Morosini’s cold state instantly warms up as “Becca” (his projection of her) cuddles close, speaking the fumbling, sometimes sincere words from Chuck behind his laptop and phone. With key intercuts that play like punchlines—without getting redundant—we remember the truth behind these moments of comforting fantasy for both the son and the father. This approach makes its awkward comedy all the more visceral, like when Franklin wants to text-kiss “Becca”; we see what a wincing Chuck is feeling, as his son Franklin appears in the room, starry-eyed and ready to lock lips. All of this is to say that the comic MVP of this movie is not Oswalt, or even actor/writer/director Morosini, but Claudia Sulewski. Her character can sometimes be an avatar for Oswalt, saying his words in her own voice with great comic timing; in other lenses she is an all-game fantasy for Franklin (at one point walking on the water of swimming pool). Sulewski plays into both “Becca” exaggerations so thoughtfully, that by the third act her actual Becca has a special poignancy and agency—a kind server at a Maine restaurant who has been brought into a disturbing family mess, and also has had her identity stolen. Her performance helps create the movie’s essential whiplashes of fantasy meeting reality. There proves to be a lot of character-based comedy to go around with this concept, so much that “I Love My Dad” can get close to underusing certain pieces of its great ensemble. Amy Landecker is funny but too briefly seen as Franklin’s mother Diane, who eventually becomes aware of her ex-husband’s horror show; Rachel Dratch is punchy as Chuck’s current girlfriend, another person he tries to manipulate. At least Lil Rel Howery, one of the hardest working supporting actors currently in Hollywood, becomes more than just the reactionary friend. He has enough head-shaking scenes opposite his co-worker Chuck, including one of the film’s best lines: “This is incest!” In his second directorial project, Morosini displays a sharp knowledge of how to use pacing and tone to their advantage when telling a story that’s otherwise filled with a staggering amount of hurt. The script puts us right into a series of progressively awkward conversations, which then hilariously parallel the one-in-a-million love story that Franklin thinks is unfolding on his chat screen (and not over video chat, because “Becca”’s camera is mysteriously always broken). All of the darker elements (Franklin’s mental health, Chuck’s gross manipulations) are handled with assurance, and embraced equally for their tragedy and honesty. It all gets squirmier and funnier the more out of control its premise becomes. I was able to see “I Love My Dad” in a theater, and I couldn’t recommend the experience more: its undulating discomfort from such sharply executed sequences are best appreciated with a bunch of shocked others in the dark. There is something so exhilarating about a comedy that’s in full control of its jackpot premise. And by treating nearly everything and everyone with such care, Morosini gives the audience layers to choose from, like the psychoanalysis of just how misguided Chuck is, or recognizing the depths of our need to feel truly seen by someone else, even just via a text bubble. “I Love My Dad” is the kind of story that doesn’t overthink what makes it so laugh-out-loud funny, but there’s a whole lot of ugly, extremely human things going on each time its comedy makes you cover your eyes. Now playing in theaters.