Ask any stand-up comedian today who the best stand-up of all time is or was, and they’ll likely tell you Richard Pryor, George Carlin, or want to make cases for both equally as the top of the tops.

Ask any Jewish comedian from the Baby Boomers through Generation X that same question, and they’ll quickly put Robert Klein right up there with them.

Klein, now 75, is the subject of his own documentary, Robert Klein Still Can’t Stop His Leg, which premiered last March at SXSW and debuts on the smaller screen tonight via Starz.

Here’s the trailer:

How about those testimonials.

Jerry Seinfeld on Klein: “He was the Beatles of comedy to me.”

From Jon Stewart: “He changed what it meant to be a comic, kind of this idea of the craft of deconstructing your experience.”

From Richard Lewis: “If I couldn’t be that fearless, what’s the point?”

What really set Klein apart from his contemporaries, though, was his consummate showmanship. He sings in almost every show, and in every one of his HBO specials, dating back to the very first stand-up special Home Box Office ever broadcast back in 1975, Klein has sung about how he could not stop his leg from moving. That bit, it turns out, came to him in a moment of improvisation one night at the original Improvisation in New York City. Even long before that moment, Klein had sung his way onto television, as early as 15 performing with his teen-aged doo-wop group on Ted Mack & The Original Amateur Hour in 1957.

Directed by Marshall Fine, Robert Klein Still Can’t Stop His Leg belongs in your catalog of essential comedy documentaries alongside those of Joan Rivers and Don Rickles, cataloging Klein’s rise from his Jewish Bronx childhood to Yale Drama School, to The Second City, where he performed in 1965 alongside Fred Willard, to “The Apple Tree” on Broadway, through a young mentorship with Rodney Dangerfield, teaching him the art of joke-writing and telling. You may or not remember he earned a Tony nomination for his work in the 1979 Broadway musical, “They’re Playing Our Song,” or that he hosted a late-night talk show on the USA Network in the 1980s.

Klein jokes about aging, from being married in real-life to an opera singer, to playing the old dad of the leading lady in TV and film dramas now. He’s done Broadway a half-dozen times and starred or co-starred in 40 movies, but still, into his mid-70s, he continues to work and find new gigs.

You may not know it from seeing him play the mayor of New York City in two Sharknado TV movies, but in the world of comedy, to many comedians you look up to, they look up to Klein as their mayor of comedy.

His first two albums, “Child of the 50’s,” and “Mind Over Matter,” established his role in comedy as a leader in processing his own life story in a humorous way that others not only could relate to and laugh about, but also inspire other comedians to mine their own stories for laughs. Pryor and Carlin might have pushed the linguistic and emotional boundaries of comedy to new heights in the 1970s and beyond, but it was another comedian who came of age in the 1950s who provided a more attainable blueprint for many comedians to follow.

Robert Klein Still Can’t Stop His Leg premieres tonight on Starz.