Cypress Hill are playing a gig with the London Symphony Orchestra — all because of a 28-year-old joke from 'The Simpsons'

• Cypress Hill and the London Symphony Orchestra will perform "Black Sunday" at the Royal Albert Hall.
• The collaboration has been 28 years in the making following a 1996 episode of "The Simpsons."
• Wednesday's performance coincides with the album's 30th anniversary.

It's taken almost three decades, but Cypress Hill and the London Symphony Orchestra will take to the stage on Wednesday for an orchestral rendition of the "Black Sunday" album, which features the hits "Insane in the Brain" and "I Wanna Get High."

The one-off gig at London's Royal Albert Hall was sparked by a joke in a 1996 episode of "The Simpsons" titled "Homerpalooza." In the episode, Cypress Hill mistakenly booked the LSO for a performance, "possibly whilst high."

After mulling a collaboration for years, the hip-hop group — the first rap act to be given a star on the Hollywood Walk of Fame — contacted the orchestra on social media.

B-Real (aka Louis Mario Freese), one of the two lead rappers in Cypress Hill, told BBC News that performing at the Royal Albert Hall is "one of those checklist moments — it's very special for us."

The rehearsals had one or two miscommunications: some members of the orchestra thought a "glock" was a reference to a glockenspiel, rather than a gun.

"We salute 'The Simpsons' because if they hadn't written the episode, we probably wouldn't have been doing this," B-Real told BBC News.

In the episode, Homer attends the "Hullabalooza festival — a play on Lollapalooza — in a bid to prove he's cool and hangs out with acts including Cypress Hill and the Smashing Pumpkins.

Rock legend Peter Frampton is responsible for trying to book the orchestra in the episode. He's been invited him to the Royal Albert Hall show, but it's not clear if he will attend.

The collaboration follows a string of predictions in "The Simpsons" that later came true, including Donald Trump being elected president, and magicians Siegfried and Roy being attacked by one of their tigers on stage.

The Simpsons was created by Matt Groening and first aired on Fox in January 1990. It's since notched up 35 seasons, making it one of the longest-running scripted prime-time TV shows.