“Sherman’s Showcase” boasts a slew of famous guest stars including John Legend, Quincy Jones and Nigel Lythgoe.

And if you’re wondering why you never heard of the series, that’s because it doesn’t exist in the real world. “Sherman’s Showcase,” premiering Wednesday (10 p.m.) on IFC is produced by Legend and created by Emmy-winning “Late Night with Jimmy Fallon” alums Bashir Salahuddin and Diallo Riddle. It’s a half-hour sketch-comedy which chronicles the history of a fictional ’70s and ’80s music/variety show hosted by the fictional Sherman McDaniels (Salahuddin).

“The idea came from a couple of places,” says Riddle, 42, who met Salahuddin when they were both in the same acapella group as Harvard students. “I remember one time we had just come offstage at ‘Fallon’ [and] we had done a sketch where Bashir looked like James Brown and I looked like one of his backup singers, and we sang all these songs about space to the tune of old R&B. I was like, ‘That was so much fun, how can we do this more often?’ That was the first inkling of the idea.”

Each episode of “Sherman’s Showcase” takes the viewer through instances in Sherman’s life and the history of his show, including segments on fictional musicians who got their start on “Sherman’s Showcase” and the history of its background dancers. It even has fake commercials a la “Saturday Night Live.”

“The devil really is in the details,” says Salahuddin, 43. “In some ways it’s a send up of a classic music dance show — ‘Midnight Special,’ ‘American Bandstand,’ ‘Soul Train.’ But because we picked that structure, dance variety … we can do sketches about the ’60s, ’70s and ’80s. It gave us the skeleton onto which we could hang bits and music covering any part of human existence.”

Salahuddin says they didn’t have to research the history of music, since it’s been part of their lives for so long, from their days in college to their stint on “Late Night” from 2009-2011.

“If you were to go to ‘Late Night with Jimmy Fallon’ in 2009, if you went into the band room on the sixth floor, you’d see Diallo and Questlove arguing about who gave James Brown the specific sound on his drums or who was playing bass in Bowie’s band in the late-’70s,” he says. “There’s a vein of incredible musical nerd-dom that is who we are. Luckily for us, we picked a show that lets us make sketches about it and have fun with a thing we already love to death.”

The pair had no trouble getting Legend on board as a producer. He also appears as himself on the show, musing about Sherman and his impact on the music industry.

“We had been friends with John Legend for years,” says Riddle. “And we said, ‘John, work with us on this music-based comedy show, we got the idea for you.’ He wrote back in a simple e-mail: ‘Let’s do it.’ So we were off and running.”

From there, they stacked their bench of supporting players with big names including Tiffany Haddish, Common and Damon Wayans Jr.

Salahuddin says that during their time at “Late Night, “we discovered that there are many musicians who really want to show you that they can be funny, too.”

For instance, Common surprised them with his comedy chops when he guest-starred in an episode.

“I liken it to the early seasons of ‘SNL,’ when Lorne Michaels was like, ‘We’re going to get Albert Brooks to do a short film, we’ll get this guy Jim Henson who’s a buddy of a buddy to come deal with these puppets, but he calls them Muppets,’ ” says Salahuddin. It wasn’t even all comedy. It was all the coolest things happening in and around Manhattan and LA, and [Michaels] was putting them on that stage.

“Similarly for us, we want ‘Sherman’ to feel unbound and chaotic — so one episode you might see Tiffany Haddish eating soup [and in] another episode you might see Quincy Jones doing jokes.”