Bill Skarsgard's portrayal of Pennywise in It is nothing short of iconic, but director Andrés Muschietti almost took the two-movie series in a completely different direction by considering Oscar-winning actress Tilda Swinton for the dancing clown. While scheduling conflicts prevented Swinton from even auditioning for the role, her participation could have led to a more book-accurate depiction of the character.
The Stephen King creation is one of the most notorious villains in all of horror literature and cinematic history as It is the literal embodiment of fear. Pennywise preys on the youth of Derry, Maine, and specifically targets the group of teens at the center of It. Pennywise continues to torment them well into adulthood, proving the long-lasting fear that the character is capable of invoking in his victims.
The most chilling aspect of Pennywise is that he appears to his victims in the form of what they fear most. Since clowns are a commonly-shared societal fear, that's the form It's Loser's Club tends to see him as. Because of that, every adaptation of the horror novel cast a male actor in the role. However, the book's ending reveals that Pennywise is, in fact, a female creature, further proving why Swinton would have been perfect for the role in ways outside of her substantial talent.
In the novel's finale, the grown-up Losers find eggs in the Derry sewers. They are subsequently introduced to Pennywise's true form — a pregnant, spider-like creature. The gender-bending aspect of Pennywise was left out of Muschietti's movies, as it'd probably be too complicated to explain without adding to the movie's already substantial run time. Many elements of It are a little out there — for one, Pennywise's mortal enemy is a massive, ancient turtle. Some things just wouldn't translate well from page to screen, and King's book is so long that some sub-plots and other background elements had to be left out.
Swinton's casting could have been a nice nod to Pennywise's somewhat gender-bending status in King's epic novel without further confusing audiences. The actress has gained a reputation for playing androgynous characters in the past as well, such as Doctor Strange's The Ancient One and Constantine's Gabriel. Her look transcends social gender constructs and has an other-worldly aspect to it, mirroring Pennywise's own origin story. Original Pennywise actor Tim Curry brought a wickedly dark sense of humor to the role in the 1990 miniseries. Skarsgard made the role his own by turning it into something deeply unsettling. As she was never cast in the role, it's impossible to say what Swinton would've brought to the part of It's Pennywise. However, it's safe to assume she would've made it unforgettable due to her ability to fully inhabit characters in unique, fascinating ways.