Twenty years on from its original West End premiere, Wicked still very much holds space in our hearts.

Now a bestselling book series, a theatre show in more than 130 cities worldwide, and two record-breaking movies that blew up the internet, the story really has had a gravity-defying impact on us and the musical genre.

It's safe to say Elphaba and Glinda's story of friendship has become universally known, as have the hit songs like For Good and Popular, the sets and even the side characters. But even if you think you know Wicked down to the details on Cynthia Erivo's index finger, there's still some things that might surprise you.

So, in honour of 20 years on the London stage, we've compiled 20 wild and wonderful facts about Wicked. How many did you know?

1. The Wicked Witch wasn't originally the subject of Gregory Maguire's inspiration

Despite the obvious source material, Wicked wasn't originally inspired by The Wizard of Oz at all. Author Gregory Maguire was interested by the way media in the '90s started using the word 'Hitler' as a shortcut for 'evil'. He therefore wanted to write something philosophical about the roots of evil and whether a person is born bad or shaped by society. After deciding that Hitler was far too big a historical subject to tackle, he turned instead to fictional characters who popular culture loathed, and landed on L Frank Baum's Oz and the iconic green-skinned villain of the Wicked Witch of the West.

2. The Wicked Witch of the West's name comes from The Wizard of Oz author

The Wicked Witch is never given a name in the original Oz books. So, in 1996 when Maguire wrote Wicked: The Life and Times of the Wicked Witch of the West, he used L Frank Baum's initials – LFB – from which he coined Elphaba.

3. The original novel is much darker (and stranger) than the musical

Where to begin on the differences between Maguire's four Wicked novels and the musical? If you're unaware, the books have a much more adult feel to them and aren't necessarily aligned with fans of the musical. To start, the gaps in time are bigger, so much so that by the time Fiyero and Elphaba reunite, the Prince is married with three kids and has an extra-martial affair with Elphaba. The Wicked Witch also lives closer to her namesake, she's far more radicalised by the politics in Oz and creates the Flying Monkeys on purpose as part of an experiment, she also accidentally kills Fiyero’s young son, Manic, by knocking an icicle loose.

The novel is also a lot more graphic in both deaths and sex. Doctor Dillamond is brutally murdered by Madame Morrible's goons and all book fans know about the infamous Philosophy Club – a psychedelic sex club attended by Shiz University students. One of Elphaba's social circle, Tibbett, contracts and eventually dies from an unspecified illness at the club (thought to be through intimacy with a tiger).

4. The musical was dreamt up while Stephen Schwartz was in Hawaii

Composer Stephen Schwartz was snorkelling in Hawaii when a friend recommended him the Wicked novel. "It was like a little bell went off in my head," Schwartz recalled, and so when he returned home, the first thing he did was call his lawyer to obtain the rights for a Broadway musical.

5. The show was originally meant to be a film first

Upon returning from his trip, Schwartz discovered that Maguire had already sold the rights to Universal Studios, which was developing it as a live-action movie. Driven by his instinct that the story belonged on stage, Schwartz made a plea to producer Marc Platt (Ben Platt's father), convincing him that it needed to be adapted into a theatrical musical instead.

6. Glinda wasn't originally supposed to be nearly as important to the show

In the books, Galinda/Glinda is a much more peripheral character – it's Elphaba and Fiyero's relationship that sits at the centre. However, Stephen Schwartz saw the potential in turning the musical into a story of teen female friendship, so worked with Winnie Holzman to turn the Good Witch into one of the two main roles. Yet he also wrote the part for Kristin Chenoweth herself. Her personality and comedic timing helped shape the character and Chenoweth was the one to come up with Glinda's iconic 'la las' in the song Popular. She said she'd imagine Glinda "in her room growing up. She probably loved ballet. She was a girly girl."

7. Idina Menzel actually cracked the big note at her Elphaba audition

Before Cynthia Erivo, Idina Menzel was absolutely synonymous with the epic notes of Defying Gravity, which makes it even more surprising that she botched it on the first audition. Recalling in an interview with Vogue, she said: "I practised the really high note, and I got to that part, where you go, ‘You won’t bring me down,’ and I was singing beautifully the whole time, then I got to, ‘You won’t bring me,’ and I choked."

“I just said the F-word so loud at the top of my lungs, and then I looked at the accompanist, like ‘Don’t you start to play on or cut me off!’ and then I took a deep breath and I went: ‘Meeeeeee,’” she recalled. “And I just nailed it!” She added, “That’s when Joe Mantello said I got the role, because he thought I was just so evil and witchy.”

8. The famous riff in Defying Gravity almost didn't exist

Thank god she did get the part because the famous final riff in the song is all down to Menzel. In rehearsal the song was developed around Menzel's performance and Chenoweth later recalled that the notes weren't explicitly written until Menzel joined the production, and so she brought in that much-loved moment that now lives on forever.

9. Neither did Fiyero's big song Dancing Through Life

Imagine a world where we wouldn't have seen Jonathan Bailey's Dancing Through Life – it almost doesn't bear thinking about. But it's true, Fiyero was first introduced with a song called Which Way's the Party?, but producers felt it didn't explain the prince's character well enough.

10. Glinda's blue dress was inspired by Princess Diana

It's no surprise the Wicked movies won best costume design at the Oscars because the theatre show had already laid an excellent groundwork. Take Glinda's iconic blue bubble dress which was inspired by Queen Elizabeth II’s coronation, Princess Diana’s wedding, and in particular, Dior’s Junon Gown from the 1949–50 fall/winter collection. The dress weighs about 14 pounds, contains 64 petals and requires 68,200 blue and white hand-sewn sequins.

11. Elphaba's famous green skin comes from a high-street brand

Elphaba's green skin comes from the high-street beauty brand MAC. If we're getting specific it's the Chromacake in Landscape Green which is applied using a paintbrush and a mixture of the Chromacake and water. In a video for the Wicked YouTube page, make-up designer Joe Dulude II said: "The whole point was to make it look like skin, not look like make-up." The same thought was key for Cynthia Erivo's look in the movie so make-up supervisor Frances Hannon used a highlighter-yellow undertone to make sure the green looked real and reflected light instead of absorbing it on camera.

12. The show has a massive quick change with 17 actors in under a minute

In the first act, the theatre production sees an ensemble of roughly 17 actors change from the mob in No One Mourns the Wicked to students for Dear Old Shiz. They reportedly only have about a minute and a half to change, which includes changing costumes, wigs and shoes.

13. The lyrics of For Good come from Schwartz's daughter's real friendship

The final song of Wicked, For Good, has made millions of people cry because of how it depicts female friendship. How fitting then that it came from the actual friendship of Schwartz's young daughter. In an interview with CBS, Schwartz said he asked daughter to help with some of the lyrics: "I went to Jess with a yellow pad in hand and said, 'I want you to imagine that you're never going to see your friend Sarah again, and you have one chance to tell her what she means to you. What would you say?'"

14. Just one day before her final performance, Idina Menzel fell through a trap door on stage

Idina Menzel's final weekend playing Elphaba on Broadway was slightly marred when an elevator beneath the trap door Menzel would normally step on during the show's melting sequence began to descend without her. As a result, Menzel fell through the door and earned a cracked rib in the process. The show was stopped until her understudy Shoshana Bean could finish the performance and the next night – what would have been her final performance – she was instead brought on to take a final bow in a red tracksuit.

About that fall, Menzel later wrote: "So I melted every night and this time, I guess I really melted. It wasn't the farewell I had in mind, but thanks to all of you and the incredible company, it was a truly special evening for me. It would have been nice to sing those songs one last time, but somehow, after that night, I still feel a sense of completion and I am at peace with that."

15. Two of the original Broadway cast met and married during the show run

Norbert Leo Butz, who played Fiyero, and Michelle Federer, who played Nessarose, acted as part of the original Broadway cast of Wicked and later married in 2007. The pair are still married and share three children together. At the time, Butz joked to Broadway.com that he won over Federer with Fiyero’s tight white pants in the show, quipping that “she was checking out those white pants when I was Dancing Through Life. Now she’s dancing through wife!”

16. Judy Garland is honoured in Defying Gravity

Judy Garland's spectacular legacy is honoured throughout Wicked. For one, nothing of her character is changed, in fact she's hardly seen except a few back-of-head shots in the Wicked movie, thus leaving Garland's version intact. For another, Schwartz wrote the notes of Somewhere Over the Rainbow into Elphaba’s recurring use of the words "unlimited / I’m limited" to evoke the same sense of lifting up.

17. It's a powerful show... literally

No, literally! Every single performance of Wicked uses enough electricity to power 12 homes. The show also uses 250 pounds of dry ice to create the impressive fog.

18. And it's had stratospheric success... literally

Never has a song use been more apt than when NASA played Defying Gravity as a wake-up call for an astronaut completing a space walk in 2010. The song was used for Dorothy “Dottie” Metcalf-Lindenburger during a Space Shuttle Discovery mission on the STS-131.

19. The Wicked film actually planted 10 million tulips for the opening shot

In the first Wicked movie, a tulip field near King's Lynn in Norfolk was featured as a backdrop to Munchkinland, with a whopping nine million bloomed for the blockbuster. Except, 10 million were actually planted. Production designer Nathan Crowley revealed: "We had to hide the yellow tulips in the field next door – three fields over. We actually planted 10 million tulips, nine coloured and one giant field of yellows."

20. The show has smashed dozens of records

As we reflect on 20 years of the show, it's worth a reminder: the show has been seen by more than 13 million people in London alone, and 70 million worldwide. The first Wicked movie was the biggest Broadway-to-screen opening ever, earning $114 million domestically and $164.2 million worldwide, only to be smashed by its second movie, $150 million domestic and $226 million global. The stage production has grossed over $6 billion globally across performances in 16 countries and six languages and, we're sure, it will run for another 20 years.

Make sure you also check out our Hamilton behind the scenes secrets and Les Misérables backstage secrets.