Warning: this article contains spoilers for the upcoming film Wicked: For Good.

Wicked fans are in an uproar after actor Ethan Slater shared what many consider a spoiler from the upcoming sequel on his Instagram profile.

The grand finale to Jon M. Chu’s adaptation of the stage hit Wicked, originally based on the 1995 novel by Gregory Maguire, is set to premiere this November.

The continuation of Elphaba Thropp's (portrayed by Cynthia Erivo) and Glinda Upland’s (Ariana Grande) journey, titled Wicked: For Good, includes beloved characters returning, such as Jonathan Bailey as Prince Fiyero and Slater as Boq Woodsman.

However, Slater has found himself in a predicament with fans before the film's release by posting a scene from the movie on social media.

After the final Wicked: For Good trailer dropped yesterday (September 25), the 33-year-old actor shared an image from the movie musical with his 246,000 Instagram followers.

The two black-and-white photos confirmed his transformation from Boq into the enigmatic Tin Man, who made a brief appearance in the video teaser.

"What have you done to me?” the actor’s character is heard exclaiming.

Both the official clip and the images Slater shared have caused a stir on social media, with many accusing the father-of-one and Universal Pictures of ‘spoiling’ the Wicked: For Good storyline.

"I’ve never seen the musical (and won’t until I’ve seen part 2 movie) and I feel like I’m getting spoiled. I don’t even watch any trailers lmao,” expressed one X user.

Another remarked: “I understand that spoilers might be hard to avoid, but seriously."

Ethan Slater has confirmed he will be transforming into the Tin Man in Wicked: For Good (Instagram/ethanslater)

“Why would you spoil the twist for those who haven't seen the play?” another questioned.

Referring to the fact that Wicked debuted on Broadway in October 2003, another X user wrote: “You’re all talking about spoilers, and it’s a 20-year-old musical, oh please.”

Someone else echoed: “For those upset about spoilers, it's an adaptation. It's not a spoiler if it’s based on a well-known existing work.

“That’s like claiming it’s a spoiler to say Mufasa dies in The Lion King. People can discuss publicly known events from 20+ years ago.”

A third added: "Yes. You cannot spoil an adaptation, especially one that’s two decades old. The concept is absurd and frankly on those who get upset about it. They should’ve read the book/comics beforehand. Before the Hunger Games came out, I read the series to appreciate and understand what I was about to watch."

Wicked fans have been debating whether the reveal is a 'spoiler', considering the book came out in 1995 and the play in 2003 (Universal Pictures)

It appears, however, that Slater wasn't the first to disclose his transformation into the Tin Man in Wicked: For Good.

In January, the film's hair and makeup artist Frances Hannon discussed his transformation, revealing to VFX Voice that the look was achieved using a mix of practical and CGI effects.

“For Tin Man, we aimed for a sympathetic appearance because it should have never happened to Boq,” Hannon explained.

“In our story, Elphaba’s spell goes awry in Nessarose’s office, and everything metal in the room clings to Boq; his breastplate becomes the tray on the table, and his hands turn into thimbles, salt, and peppers. Then, visual effects took over because all the joints were blue.”

The theatre favourite played Boq in the first Wicked film (Universal Pictures)

Earlier this month, Slater shared insights into returning to the Wicked universe with Fandango.

He shared: “It was exciting to delve deeper into Boq and Nessa's relationship and spend more time exploring it.

“[We illustrate] how things get distorted over time.”

The character of the Tin Man has appeared in numerous adaptations and sequels since his introduction in L. Frank Baum’s 1900 book, The Wonderful Wizard of Oz.

In addition to appearing in the Oz books, he has featured in an episode of Once Upon a Time, the 2007 miniseries Tin Man, and even in The Muppet’s Wizard of Oz.

If you really want to understand what will happen to Boq and his friends in the upcoming film, you can read the book.

Wicked: For Good is scheduled for release on November 21.