Comic genius Jonathan Winters is the star of Certifiably Jonathan, a mockumentary featuring several notable actors and comedians.

Wacky comedian Jonathan Winters, who kept America in stitches for more than a generation from the 1950s to the ’80s, is the funny heart of Certifiably Jonathan, writer-director Jim Pasternak’s weirdly offbeat mockumentary which is showing tomorrow and Sunday at the Rhode Island International Film Festival.

With his deadpan delivery of outrageous lines and his oddball characters and voice, Winters was a mainstay of TV variety shows, from Jack Paar’s late-night gabfest in the early 1950s to Ed Sullivan to the Smothers Brothers. “Did you ever undress in front of a dog?” he asks an audience in one of the old black-and-white recordings of TV shows that occasionally surface in the film. “A bird somehow doesn’t count. Or a cat,” he continues to the audience’s laughter. “But a dog,” he says, pausing to let the anticipation build, “they really stare.”

At 80 in Certifiably Jonathan, Winters shows he hasn’t lost his punchiness nor the slightly weird way he has with some of his made-up characters. It’s his edginess that puts this film into a realm of its own, making one wonder at times whether Winters is just kidding or is about to actually go around the bend.

Certifiably Jonathan revolves around Pasternak trying to make a documentary about the comedian’s attempts to get a showing of his paintings at the Museum of Modern Art in New York and how, once that unlikely feat is nearly accomplished, it is derailed.

The comic’s paintings are mainly simple stick-like figures or complex designs on brightly colored backgrounds with unusual themes. Two Birds Watching Doris Day’s Cat and Dog Drown, Crazy Old Lady With Sunburned Boobs, An Evil Woodpecker and A Tree in South Boston are some of his works, the latter with a red tree at the center, its branches on one side covered with colorful birds, the other side graced by a single black bird.

Pasternak persuades an authoritative critic from an international art magazine to look at Winters’ paintings. Surprisingly, he pronounces them great works, a bridge between Miro and Dali. This leads to a promised gallery show at MoMA, but only if Winters can come up with three new and very large paintings for the exhibit.

But what should be a joyous moment is soon shattered when someone steals Winters’ favorite painting from a Beverly Hills gallery, sending him into a funk. He says he has lost his sense of humor after this event, claiming it was stolen by a witch doctor who accosted him in a bathroom “and sucked the humor right out of me.” He is so depressed that he cannot paint, not even for MoMA. At one point many years ago, Winters’ real-life depression led to a nervous breakdown that got him committed to a mental institution, a part of his history that Winters references more than once in Certifiably Jonathan. In the film he describes himself as “a man of many moods,” one who’s “very happy with my insanity.”

Certifiably Jonathan, which had been brightly offbeat to this point, turns very strange as Winters clams up, looking like the walking dead and consulting a string of charlatan “humor therapists” in hopes of getting his jolliness back. He attends a séance with the assembled Arquette family — Roseanna, Patricia and several others — hoping to enlist the spirit of the late Cliff Arquette, who played folksy comic Charlie Weaver on TV, in the effort. He hires a Russian hit man to find the man who has stolen his humor. He has Howie Mandel take him to Target where they ask shoppers where they might find an aisle containing humor. Somewhere in here, Certifiably Jonathan threatens to lose its sense of humor, too.

But there are enough daffy moments to keep it afloat right to a very satisfying end. Along the way there are famous faces besides the Arquettes and Mandel — Rob Reiner, Jeffrey Tambor, to whose home he brings all his paintings for safekeeping and then refuses to leave; Tim Conway, Sarah Silverman, Nora Dunn. Robin Williams turns up again and again for some funny back-and-forth with Winters. They provide comic touches that take Certifiably Jonathan to unexpected places.

Certifiably Jonathan will be shown at 7 p.m. today at the Courthouse Center for the Arts, Route 138, Kingston, and at 7:15 p.m. tomorrow at the Columbus Theatre, 270 Broadway, Providence, as part of the 12th Rhode Island International Film Festival. Tickets are $10 at the door. For a complete schedule of films see rifilmfest.org.

*** 1/2Certifiably Jonathan

Starring: Jonathan Winters, Robin Williams, Roseanna Arquette, Patricia Arquette, Rob Reiner, Jeffrey Tambor, Nora Dunn, Tim Conway, Sarah Silverman.

Rated: Not rated, contains adult themes.

mjanuson@projo.com