As far as unlikely band reunions go, Dr. Octagon’s was the unlikeliest of them all.

The oddball hip-hop collective barely held it together the first time around when it released its genre-shifting 1996 debut, “Dr. Octagonecologyst,” a sci-fi concept album with a horror movie soundtrack that sold some 200,000 copies without any touring or significant promotion on the artists’ part.

The release turned out to be a one-off, but a little over two decades later, the players — producer Dan “the Automator” Nakamura and turntablist Richard “Qbert” Quitevis, both from San Francisco, and former Ultramagnetic MCs rapper Keith “Kool Keith” Thornton from New York — have reunited to mark its 20th anniversary by performing the album live for the first time.

There are just two dates on Dr. Octagon’s schedule for now: Monday, March 6, at the Independent in San Francisco and Tuesday, March 7, at the Telegram Ballroom in Los Angeles.

“Right now, we just want to let people know we exist,” says Nakamura, a San Francisco native whose post-Octagon production credits include Cornershop, the Jon Spencer Blues Explosion and Gorillaz. “There will be more shows.”

It’s an important step. During the critical months after “Dr. Octagonecologyst” was initially released — a deluxe box set featuring three LPs and bonus cuts from the original session is on its way — it was hard to gauge from the outside just how much Dr. Octagon was a functioning unit.

Apart from all the band members having individual projects, Thornton was particularly hard to pin down. Almost as soon as the band signed with DreamWorks, he vanished.

“It wasn’t a question of how long it was going to last. Once it started to turn, I instinctively knew there might be a clock on it,” Nakamura says. “Once he got some money in his pocket, he got a bunch of other stuff thrown in front of him. He was in the business longer than me — this was his break and he just took off. I’m not going to begrudge someone else making money.”

Thornton returned to the spotlight over the years under a variety of different guises: Black Elvis, Dr. Dooom, Rhythm X, Mr. Gerbick, Keith Korg, Robbie Analog, Matthew and even with his own version of Dr. Octagon, with live performances fueled by graphic videos and members of his crew throwing fried chicken out into the audience.

But none of his work brought him the same acclaim as his role as the cracked hip-hop surgeon who specialized in kinky, sex and sci-fi fueled lyrical misadventures.

Guided by the far-out ambient soundscapes of Nakamura — made up of elaborate hip-hop beats and a bevy of exotic live instruments — and the turntable wizardry of DJ Qbert of the Invisible Scratch Pickles, Dr. Octagon remains the perfect vessel for Thornton to spin his explicit and abstract tales or lechery.

“A lot of people probably thought I was smoking PCP and was on drugs,” Thornton, who remains elusive, says in Brian Coleman’s hip-hop tome, “Check the Technique, Volume 2.” “Other groups might have needed to be on drugs to attempt a record like that. But I was eating potato chips when we made it. Yoo-Hoos and donuts. It was one big spaceship and everyone was riding. Me and Automator were Mr. Spock and Captain Kirk.”

In songs like “Real Raw” and “Girl Let Me Touch You,” the rapper takes hip-hop’s most diabolical tendencies to biologically gritty extremes.

“We all got an adrenaline rush off what was going on,” Keith recalls in the same interview. “We were giggling as we were making the tracks because we knew that people were going to trip out on them. It was like we was at a house party and we was making a punch out of lemonade, Pepsi and Welch’s grape soda. We was putting everything inside the container: apples, greens, peanuts, cabbage. We blended it all together, and we knew people were going to bug out when they tasted it.”

The disc, originally released on Nakamura’s independent Bulk Recordings imprint, quickly became an underground hip-hop classic after its release, spawning a club hit with its first single “Blue Flowers.”

“There’s a bit of unfinished business,” the Nakamura says. “I was bummed when we couldn’t hit the road, but I’m happy with the way things worked out. It changed my whole trajectory.”

And he says Thornton is more dependable these days, particularly after seeing Octagon’s cultural legacy winding through work by contemporary artists like Kanye West.

“Me and Keith have been toying around with the idea of doing this for 10 years,” Nakamura says. “Once he got serious about doing it, we were like, ‘Let’s just do it.’ We just had to figure out a way to make it work.”

Aidin Vaziri is The San Francisco Chronicle’s pop music critic. E-mail: avaziri@sfchronicle.com Twitter: @MusicSF

Dr. Octagon: 9 p.m. Monday, March 6. The Independent, 628 Divisadero St., S.F. www.ticketfly.com

To see the music video for “Blue Flowers”: www.youtube.com/watch?v=V9VYzNUXGDA