John Krasinski changed the design of the creature in 'A Quiet Place' at the very last minute.
The 38-year-old actor has made his directorial debut with the new horror movie, and although he had designed a monster that he loved, he realised in post-production that his original design wouldn't work and was forced to change it.
Speaking to Collider, Krasinski said: "It's true. I had designed this creature and we loved him and we had so many detailed things, like drawings and boards and things for the kids to look at.
"And then it was really deep in the post [production] and it was one of those moments where, this sounds super nerdy but I now understand when people talk about visual effects and seeing this, you can just see he wasn't going to work as well as a different design.
"When you looked at the scenes and the shots that we were gonna put him in, it just didn't look like it was gonna work."
Krasinski was forced to contact the design company ILM and luckily because they were fans of the movie they agreed with his changes.
He said: "So I made the very last minute, and very horrible decision, calling ILM after they had done all this work and being like, 'So that isn't gonna work, let's move in a completely other direction'.
"And because they loved this movie so much, they went with it and they totally understood. And I will say to their credit, they have always said, 'You made the right decision. The other guy was cool, but this guy is way better'."
The new film - which stars Krasinski with his real-life wife Emily Blunt - follows a family of four who must live life in silence while hiding from creatures that hunt by sound.