The Blues Brothers were not supposed to be anything more than a fun Saturday Night Live skit that incorporated a couple of cast members and the house band.

It turned into a national phenomenon, two best-selling albums, a record-breaking live recording, one of the best musical movies of the '80s, and a chain of music venues.

The not-ready-for-prime-time bit began humbly as a humorous way for John Belushi to showcase his mediocre but sincere ability to sing Chicago Blues.

First dressed as a bee on January 17, 1976; and then more than two years later alongside Dan Aykroyd with the now-trademark black Ray Bans, trilby hats, black suits and sideburns.

For as funny as it was to watch Belushi do shockingly good cartwheels and Aykroyd hold his own on harmonica and white bread dance moves, the secret weapon of the Blues Brothers was the all star band.

Led by musical director Paul Shaffer on keyboards (who assembled the outfit) were Stax Records sessionmen guitarist Steve Cropper and bassist Donald “Duck” Dunn who you know from Booker T & the MGs' "Green Onions;" SNL bandmates Lou Marini and Tom Malone on horns alongside trumpeter Alan Rubin; the muscular Matt “Guitar” Murphy on another guitar and Steve Jordan on drums.

The April 22, 1978 appearance was a hit and special guest host Steve Martin saw it with his own eyes. Even though they only played two songs, it was painfully obvious there was something there in Belushi's performance that was so different than his Samurai or No-Coke-Pepsi SNL characters

Then a few months later, John Landis' Animal House was released and Belushi was suddenly a movie star as well.

So what's the right move? That's right, get the band back together, fly to LA and open for Steve Martin who was performing a night of stand-up at the Universal Amphitheater, and what the heck, record it.

How does the opening band, who have never played a full set, get off recording their first real show?

As we would learn from their Landis-directed self-titled 1980 film, they were on a mission from God.

Well if it wasn't God, someone upstairs liked them because they knocked out 13 covers at that first show in Los Angeles like they'd been doing it for years together.

Was it helpful that Akroyd and Belushi came from improv and then live sketch comedy of SNL, therefore knocking out a solid 45 minutes was right up their alley? Perhaps.

But the band was first rate and Shaffer was born for this sort of thing as he would demonstrate nightly with David Letterman and The Rock & Roll Hall of Fame concerts.

The band played nine shows as openers for Martin. What was recorded opening night was what became the live album, Briefcase Full of Blues.

After the September run in California, the band played Carnegie Hall in October, and returned to SNL in November. There, it was clear, they had the act down perfectly, cartwheel and all.

November saw Atlantic Records, the label that gave the world Aretha Franklin, Ray Charles, Wilson Pickett, Sam and Dave, and Otis Redding released Briefcase Full of Blues just two months after the band had truly become a band.

And once again the fates looked down on them. The first single "Soul Man" spent 15 weeks on the charts and peaked at #14.

Best of all, it wasn't a comedy take. It was a genuine cover of the Isaac Hayes / David Porter groove Sam & Dave took to #2 in 1967, except sung by comedians who are just nerdy about the blues.

The 1979 pop charts, however, were not one bit nerdy about the blues. It was about Billy Joel's "My Life" and "Big Shot" off 52nd Street which spent two months straight at #1 until Jack, Elwood, and the best cover band ever assembled picked up a summer gig in the Valley.

Briefcase Full of Blues was approaching selling over a million copies in the middle of December when they were asked to open for the Grateful Dead on New Year's Eve.

NYE Dead shows are special on their own, but this one was to close down the famed San Francisco music hall, Winterland Ballroom, home of numerous important shows including the last Sex Pistols which had taken place earlier that year.

They accepted.

Briefcase Full of Blues ended up moving 3.5 million copies, winning a Grammy, and becoming the top selling Blues album of all time.

"We had to keep this music alive, to educate a younger generation on this music," Cropper told Something Else in 2014.

"Soul and blues and jazz, those are the greatest staples that the American people have invented," Cropper said. "But there's more to it than that. Eddie Floyd and [Stax drummer] Al Jackson, they told me a long time ago: It is also about entertaining people. You are not going to be interesting to people just standing up there. They can hear that on the radio. You've got to get them swinging and swaying with you."