The story of the Del Close Marathon is the story of Del Close.

And the story of Close is ultimately the story of how improvisation grew from an art form used for acting rehearsals into an actual entertainment event in itself, and how Close spurred its expansion through his disciples who became the Upright Citizens Brigade, through to their disciples and around the world, celebrated each year in an ever-larger weekend festival in New York City called DCM.

Thank You Del, directed by Todd Bieber and executive produced by Matt Besser and Matt Walsh, held its world premiere screening at SXSW last month, celebrating both the comedy mentor and the young men and women who have followed his teachings aspiring to become memorable comedians in their own right.

And it didn’t even start with Del, specifically.

Nor did it start in Chicago.

Well, improvisation did.

But not what Del Close thought to do with it. That happened after Close already had performed with The Compass Players in St. Louis, then headed west to join The Committee in San Francisco. Who, if you ask them — and Bieber did — developed what we all know as “the Harold” structure essentially by committee. “We created long-form improv,” Alan Myers, The Committee’s founder, tells us. Sitting next to Myers, Howard Hesseman, recognizable to anyone with a TV in the 1980s from WKRP in Cincinnati or Head of the Class, adds: “Del’s story is that he created it. But he was a member of a company that created it.” Their truth holds that Close was leading the group’s workshop when they figured out a framework that could contain longer improvisational scenes, and their piano player sarcastically suggested, “Well, Harold’s a nice name.”

And just as improv comedy groups around the world do now, Close did then, begrudgingly accepting the one-word suggestion and running with it. Straight to Chicago, and also Toronto, where he directed Second City troupes for about a decade until 1982 — which if you know your comedy history, meant that he taught almost everyone you came to know and love on Saturday Night Live, SCTV and more.

The footage assembled and curated here is extensive, from showing Close teach the still young and unknown George Wendt, Tim Kazurinsky and others in Second City in the late 1970s. to the late Bernie Sahlins, Second City’s co-founder, recalling his fallout with Close. Sahlins believed improvisation was process, a workshop designed to develop the actual sketch show, and not something worth charging customers to watch in itself. Sahlins fired Close. And then Close joined Charna Halpern up the road in her new theater, the improv Olympic. There he could cultivate a generation of new comedians, teaching them harshly but also inspiring them to reach their fullest potentials.

“Most of all he always said, play at the top of your intelligence. Treat the audience like poets and geniuses, and that’s what they’ll become,” recalls Adam McKay.

Close put McKay in a group called The Family, a precursor to what would become the Upright Citizens Brigade. McKay left the original UCB to write for Saturday Night Live in 1995. The UCB4 — Amy Poehler, Matt Besser, Matt Walsh and Ian Roberts — would move to New York City a year later, and by the time Close died in 1999 at 64, the UCB4 had not only launched a Comedy Central sketch series, but also opened their own theater and school. They honored Close’s memory that year with their first all-night marathon of improv.

At DCM15, Bieber trained his camera crews on a relatively new and inexperienced troupe from Poplar Bluff, Mo., called Hi Let’s Be Friends, who’d only performed together a couple of times in their town before venturing to NYC to participate in what had become a three-day-and-night marathon, complete with other comedy collectives from as far away as Japan, Puerto Rico and Finland.

“The fact that people are doing this, and we couldn’t get eight people in the audience, and now people all over the world are doing this, it’s incredible,” says Halpern.

“When you talk about Del, it’s hard not to sound like you like groovy cult man, but like, he did start a movement, that he created a home or environment for people to kind of find themselves and who they are,” says Poehler.

Of course, some of Close’s close comrades from his earliest days wonder why the focus is on him, and not Viola Spolin, who founded The Compass Players and taught Close. Or Spolin’s son, Paul Sills, who co-founded The Second City.

Myerson: “What I’m really curious about is why people are celebrating Del, who had two great talents. One was a very inspirational teacher, and he was an incredible salesman and evangelizer. But the truth is, he was not a great creative force. Why aren’t we making movies about Paul and Viola? That’s what I want to know.”

I think he answered his own question.

As Besser explains in Thank You Del, since Close isn’t around to do so, it was Close who kept improv alive as a performing art, and his evangelism has spread and splintered across the country and the world, with even multiple theaters espousing different principles, all tied back to Close. For instance, Ali Farahnakian, seen in old footage with The Family at iO but not interviewed for this documentary, went on to found another improv theater and school in NYC, The PIT. Similarly theaters and classes and other schools of thought have popped up in Austin, North Carolina, Boston, Denver and even elsewhere in Chicago. At Close’s deathbed in a Chicago hospital back in 1999, Bill Murray hosted one last party for him, and the documentary reveals Close saying he needed to talk to Besser and the UCB. Urgent! He instructs him to carry the message. Here is some of the original raw footage:

Reflecting on it now, Poelher recalls: “It was kind of in character. It was like this kind of coded, cryptic, cool thing. And then the next day he died. Which is really cool because Del kind of knew when to edit. Supposedly his last words were ‘I’m tired of being the funniest person in the room.’”

In an interview that opens the documentary from 1988, Close acknowledged: “The kind of improvisation that I am particularly addicted to is the kind that does not aim at creating material — that aims at creating a momentary fragmentary experience that has some kind of totality to it. It’s kind of like fireworks. The most ephemeral of art forms. You know, once it’s gone.” He snaps his fingers. “It’s gone, baby. There’s the after-image for a few seconds, but nobody will ever see anything like it again.”

And that’s the beauty and the explosive madness of DCM. Even I can attest to that.

Thank You Del premiered at SXSW but also will screen this month at the Florida Film Festival, Hot Docs Festival in Toronto, and the Nashville Film Festival.

DCM18 will happen June 24-26, 2016.

Reverse angle: Witnessing the UCB unveil their book on improv philosophy at DCM15’s opening “press conference.”

Further: Vines from DCM15

Listen:

Last things First, Episode 2: Live from DCM17 with the UCB

Last things First, Episode 26: Ali Farahnakian