Image Credit: Frank Wiese/AP Images Stephen J. Cannell didn’t produce every show on television during the late 1970s and 1980s—it just seemed like he did. The Rockford Files. The Greatest American Hero. The A-Team. Over the course of a 40-year career, Cannell, who died Friday at age 69, produced more than 40 TV series. For anyone who grew up on his shows, the man and his creations simply defined television.

While it’s natural for any appreciation of Cannell’s career to begin by noting how prolific he was, a closer look at that considerable body of work reminds us that entertaining TV—and certainly long-running TV—is fueled by great characters. The Stephen J. Cannell TV Making Machine churned out one iconic TV character after another. Baretta. Jim Rockford. Every member of the A-Team. The Commish. Officer Tom Hanson… although you may know him better as “The character Johnny Depp played on 21 Jump Street.” Which reminds us that Cannell’s legacy also includes the stars he helped launch or build, from Mr. T to Ken Wahl, Kevin Spacey to Michael Chiklis. Cannell’s own take on his legacy? “All hits are basically mistakes,” the producer told EW earlier this year. “Everyone starts out desperately trying to make a hit, but some people are just more mistake-prone than others. I happened to be fairly mistake-prone. Of the 40 shows I made, I’d say ten were hits, which is a pretty good average.”

Cannell produced for an era in which TV success was still measured by total households, not demos or niches. His shows had to work for tens of millions of viewers; as such, he was a master engineer of broadly appealing entertainment. Defining characteristics: Wit, heart, resolvable conflicts, and lots and lots and lots of action. Because of this, Cannell wasn’t a critics’ darling, though it would be grossly unfair to say that his work lacked intelligence. The Rockford Files alone refutes the charge. In fact, Cannell helped pave the way for the great dramas of the past decade. Wiseguy (1987; co-created with Frank Lupo) was a smart crime drama about an undercover agent (Wahl) that took a risky approach to serialized storytelling by telling two or three distinct, self-contained sagas each season with wholly different casts. Profit starring Adrian Pasdar (1996; executive produced by Cannell but created by David Greenwalt and John McNamara) lasted just four episodes on Fox (eight episodes were produced, all now available on DVD), subverted by the very thing that has made it a cult classic and extremely influential among TV writers: the “hero” was a villain, a complex, morally muddy creep who set the stage for Tony Soprano and Dexter.

And then there was The Greatest American Hero (1981), a treasured fave (cue that theme song in your head!) for anyone who grew up geeky in the age of Star Wars, early Spielberg, and the first Battlestar Galactica, a high-concept super-hero dramedy starring William Katt and Robert Culp that dared to give us a Superman who struggled mightily to be super. Lost co-creator Damon Lindelof tells EW: “As huge a fan as I was of The Rockford Files and The A-Team, the show that really made an impression on me was Greatest American Hero. Not to get all deep about it, but the fundamental idea of a superhero who didn’t have the instruction manual for his own powers really resonated… it was such an amazingly apt metaphor for the way so many of us feel. Trust me, when we first created Lost, I would’ve KILLED for an instruction manual.”

Carlton Cuse–executive producer of Lost, Nash Bridges, and The Adventures of Brisco County, Jr.–tells EW that “one of my great regrets is that I never got to work with him…. Stephen Cannell was one of greatest writers in TV history. He understood exactly how to entertain an audience. I learned a tremendous about how to make TV through osmosis by watching Steven Cannell’s shows. Rockford is a perfectly constructed TV show of the highest caliber. And while his shows tended to be lighter in tone or action-oriented, they were always supremely well crafted.”

“I really hesitate to say that any of my shows influenced other writers,” Cannell told EW earlier this year. “We’re all mining the same fields. It’s hard for me to look at someone else’s show and say, ‘Oh, that’s from The A-Team.’ I never feel that way. But once you put something like The A-Team on the map, it does become part of the DNA of television. People grab little pieces of it. I certainly grabbed little pieces of other people’s shows when I was creating my shows.”

We remember Cannell as he would want to be remembered: As a writer. The vanity credit that concluded many of his shows became as famous as the shows themselves: Cannell triumphantly ripping a page out of his IBM Selectric typewriter; cue upbeat guitar riff. He grew up comfortable in Pasadena, dreaming of becoming an author. He struggled to get there; school was a challenge due to his dyslexia. He graduated from the University of Oregon and broke into Hollywood by selling a script for the TV series It Takes A Thief. He worked for Jack Webb Productions as a story editor on Adam-12. In 1974 NBC greenlit The Rockford Files (co-created with Roy Huggins), and soon thereafter, Stephen J. Cannell became his own boss, and then a brand. Over the past 14 years, Cannell focused his creative energies on writing mystery novels. He was prodigiously successful at that, too, authoring and co-authoring 17 titles. (A new book, The Prostitutes’ Ball, is set for release Oct. 12) The Sopranos creator David Chase, who worked as a writer on The Rockford Files, is said to have once remarked that he knew of no one who loved writing more than Cannell. As comedian Patton Oswalt tweeted today: “In memory of Stephen J. Cannell, everyone rip a sheet of paper out of your typewriter and let it fall to the ground.”

Cannell, who died from complications due to melanoma, is survived by his wife of 46 years, Marcia, their three children, Tawnia, Chelsea, and Cody, and three grandchildren. In a statement, Cannell’s family says donations in his memory may be made to the American Cancer Society or the International Dyslexia Association.

Additional reporting by Benjamin Svetkey