It was Marshall Checker, of the legendary Checker brothers, who first discovered them in the gritty blues clubs of Chicago’s South Side in 1969 and handed them their big break nine years later with an introduction to music-industry heavyweight and host of television’s Rock Concert, Don Kirshner. Actually, none of that is true, but it’s the story that Saturday Night Live‘s Paul Shaffer told on April 22, 1978 as he announced the worldwide television debut of that night’s musical guest, the Blues Brothers—the not-quite-real, not-quite-fake musical creation of SNL cast members Dan Aykroyd and John Belushi.

The characters and the band that Belushi and Aykroyd unveiled that night took more than two years to evolve. The first incarnation came during SNL‘s first season, in a January 17, 1976, appearance singing “I’m a King Bee” as “Howard Shore and his All-Bee Band.” There were no dark suits, skinny ties or Ray-Bans at that point, but the appearance did feature Aykroyd on the harmonica and Belushi on vocals belting out a blues classic very much in the style of the future Elwood and “Joliet” Jake Blues, albeit while wearing bee costumes. The Blues Brothers’ look—and much of their repertoire—would come together after Belushi’s trip to Eugene, Oregon, during the hiatus between SNL seasons two and three to film Animal House. It was there that Belushi, a committed rock-and-roll fan, met a 25-year-old bluesman named Curtis Salgado, future harmonica player for Robert Cray, frontman for Roomful of Blues and a major figure on the burgeoning Pacific Northwest blues scene of the 1970s. Belushi became a regular visitor to the Eugene Hotel to catch Salgado’s act during the filming of Animal House, and it was from that act and from Salgado himself that he picked up a passion for the blues as well as the inspiration for the Blues Brothers’ sound and look .

Back in New York for the third season of SNL, Belushi and Aykroyd honed their concept for the Blues Brothers Band and recruited an incredible roster of backing instrumentalists drawn from among the finest blues and R&B session musicians in the country. Even if their debut performance on this night in 1978 hadn’t been a huge hit, the band was far too good to break up after a single gig. Indeed, the closing portion of Paul Shaffer’s introduction that night—”Today they are no longer an authentic blues act, but have managed to become a viable commercial product”—ended up being borne out in real life, with the Blues Brothers earning three top-40 hits (“Soul Man,” “Rubber Biscuit” and “Gimme Some Lovin’”), a #1 pop album (Briefcase Full of Blues) and a piece of screen immortality via their 1980 film, The Blues Brothers.