Anya Taylor-Joy "completely died" when M. Night Shyamalan told her she was going to be in 'Glass'.
The 21-year-old actress starred as Casey Cooke in the thriller 'Split' and she admitted she had no idea her movie was linked to Shyamalan's 2000 movie 'Unbreakable', and couldn't believe it when he asked her to return for the third film because she loves her character.
She told Entertainment Weekly: "Night asked me to go to one of those tester screenings in Arizona.
"I went with him, and the ending wasn't part of that, but, as we were outside ready to go into the screening, [he] told me about it [and 'Glass'].
"I completely lost it. I thought, 'Man, that's so cool, like, you have to let me know how shooting goes!'
"He just looked at me and said, 'What makes you think you're not coming along for the ride?'
"I completely died. I was like, 'Wait, really? You want me to come and do this with you?' I was so excited to reprise my character, because I love Casey so much, and to be able to do it with all these unbelievable actors.
"I was at a table with all of these incredible people. I just thought, 'What the hell am I doing here?'"
In February, Variety reported the third movie in the now trilogy had started shooting in Philadelphia with Disney joining Universal Studios as the distributor.
The movie is being produced by Shyamalan and Blumhouse Production's Jason Blum, who also worked on the two previous films for Universal.
'Split' follows James McAvoy as multiple-personality sufferer Kevin Wendell Crumb who kidnaps Taylor-Joy's character Casey as he attempts to battle his darkest personality known as The Beast.
The surprise ending of the film shows it be a follow-up to 'Unbreakable', which starred Bruce Willis as security guard David Dunn who discovers he has super-human strength and resistance to injury.
Samuel L. Jackson played Elijah Price, who was born with Type I osteogenesis imperfecta a rare disease that renders sufferers' bones extremely fragile and prone to fracture leading him to be dubbed 'Mr. Glass' by other kids and the inspiration for his search for Dunn's character, his polar opposite.
Price is revealed to be responsible for a number of terrorist atrocities orchestrated to find a real-life superhero.
In 'Glass', Dunn will be pursuing The Beast in 'Glass' in a series of encounters.
Ashwin Rajan and Marc Bienstock will also be part of the film along with Steven Schneider who will executive produce.