Here comes Chris Farley, entering his own documentary “I Am Chris Farley” doing cartwheels. It’s his first appearance on “The Late Show with David Letterman,” and it’s utterly delightful to see how Farley charms the pants off the normally reserved, arch host (Letterman is every bit Farley’s opposite) with his physical explosions of comedy and puppy-dog excitement at just being there.

In many ways, Farley never stopped doing cartwheels, right up until his tragic death of a drug overdose in December 1997. Eager to please, almost desperate for a laugh, and fearless about how to go about getting one, the through-line in “I Am Chris Farley” is of a kid who was driven to entertain. His brother John tells the story of a fourth-grade Chris leading the school bus in a rendition of “Joy to the World” on the way to school. With his shirt off, of course.

I think directors Brent Hodge and Derik Murray and the Spike Network got a tiger by the tail when they commissioned a documentary about Farley for the cable channel, intending to make it another of its “I Am . . .” televised documentaries like “I Am Steve McQueen” and “I Am Evel Kneivel.” Not surprisingly, “I Am Chris Farley” broke loose from the original plan, as there was so much interest in Farley’s story that it ended up having 60 screenings around the country. The most memorable one was, of course, at the Orpheum Theatre in Farley’s hometown of Madison, where over 1,000 people gathered to watch the film and hear stories from Farley’s brothers John, Tom and Kevin. Chris Farley’s life was simply too big for the small screen.

If you missed it, the film is out today (Aug. 11) on iTunes and video-on-demand, as well as on DVD. (It’s a strange coincidence that it’s also the one-year anniversary of Robin Williams’ death, another comedian who seemingly had no off switch.) It’s a thoroughly entertaining and affectionate film, with family members and famous friends like Adam Sandler, David Spade, Lorne Michaels, Bob Odenkirk and Mike Myers sharing great stories about Farley.

In dealing with Farley’s addictions and untimely death, “I Am Chris Farley” is certainly no “Wired” (thankfully), going light on the salacious details of his downfall.  But, for an officially-sanctioned documentary (Kevin Farley serves as executive producer and serves as something of a tour guide in the film), the film does go deeper than I expected into the insecurities and self-loathing that underpinned both his comic genius and his vices. It’s Midwestern polite, but also Midwestern honest.

With the Farley family fully participating in the film, the documentary contains a treasure trove of old photos and home movie footage of the Farley family in Maple Bluff, Chris the middle child of five kids always looking to stand out. The Blu-ray edition includes a bonus feature with even more Madison reminiscences from Farley’s siblings.

He gets his first taste of theater at summer camp, of all places, later starting his formal training at the storefront Ark Theatre in Madison. In relatively short order, he goes from there to Second City in Chicago, and then to “Saturday Night Live” and then to movies. He never wrote his own material (even “The Chris Farley Show” sketches, which seemed so close to his true self), but everyone marveled at how he could take their material and make it golden.

SATURDAY NIGHT LIVE: THE BEST OF CHRIS FARLEY — Pictured: (l-r) Chris Farley, David Spade, Christina Applegate (Photo by NBC/NBCU Photo Bank via Getty Images)

Was it too fast a rise, too much too soon for someone who deep down felt like he didn’t deserve it? The film seems to suggest so, and that his downward slide into addiction started with his second movie as a lead, “Black Sheep,” which he felt wasn’t up to the level of “Tommy Boy.” His friends in the film talk about a darker side emerging because of alcohol and drugs (“Very sweet guy — before midnight,” Bob Saget says), and someone who would sum up his appeal as “Fat Guy Falls Down” with a self-deprecation that bordered on self-loathing. You get glimmers that he was perhaps going to mature both as a person and a performer (the recently-leaked audio of Farley’s voice work for “Shrek” suggest a satisfying second phase for his career), but he never gave himself the chance.

Kevin Farley says in the film that “Chris wouldn’t want any sadness,” and “I Am Chris Farley” tries to follow this credo, focusing on the good times and the funny stories. But the sadness is there, perhaps more than I expected, because the tragic quality of Farley’s life is so intertwined with his comedic genius and drive to always be the most entertaining force in the room.

The quote I ended up taking away from “I Am Chris Farley” comes from Odenkirk at the end of the film, who starts off as if he’s saying the usual bromide about Farley. “It’s just so rare that somebody has that much joy and brings that much happiness to everyone around them.”

And then Odenkirk’s voice takes on an edge of bitterness. “But with Chris, there is a limit to how wonderful that is. And, for me, that limit’s when you kill yourself with drugs and alcohol. That’s when it stops being so fucking magical for me.”