Bill Skarsgard is going to be your biggest nightmare come September, when he appears as Pennywise the Clown in the highly anticipated Stephen King adaptation “It.” But a producer on the film said Tilda Swinton was in the running to play the iconic monster.

“I swear to God,” producer Barbara Muschietti told Playlist. “We had a slot to shoot the movie and she wasn’t available, so she didn’t even audition. But of course, we all thought about her.”

Skarsgard came in and was eventually cast in the role, and he has since said that he’s scared the child actors on set while wearing his costume.

See Video: 'It' Terrifies in New Trailer of Stephen King Adaptation

“Bill came in and blew our socks off,” Barbara added. “Because he was doing his very own interpretation of Pennywise, very erudite…very, very familiar with the novel and with Pennywise in the novel, which for us was a huge help, because we went into the casting process with the book in mind.”

The kids that get threatened by the diabolical clown are played by Finn Wolfhard, Jaeden Lieberher, Jack Dylan Grazer, Wyatt Oleff, Chosen Jacobs and Jeremy Ray Taylor. Andres Muschietti directed.

Also Read: Bill Skarsgard's Pennywise Made 'It' Child Actors Cry on Set

While Swinton will not star as Pennywise, she will next be seen in Luca Guadagnino’s “Suspiria” and in Wes Anderson’s “Isle of Dogs.”

“It” arrives in theaters Sept. 8.