Shia LaBeouf convinced his father to sign over the rights to his life story for new movie Honey Boy by pretending Mel Gibson would be portraying him onscreen.

The Transformers star delves into his complicated relationship with his emotionally abusive father, Jeffrey, for the autobiographical film, which he wrote, but the actor admits he had to trick his dad in order to get his backing to make the project.

"I lied to him and told him that Mel Gibson would be playing him," Shia recently told U.S. late night host Jimmy Kimmel. "He signed the paperwork, then I got home, I sent him pictures, and I broke it to him. 'Look, it's not like that.' True story."

Instead of Mel playing Jeffrey, Shia takes on the role himself, portraying a younger version of his father - and his casting didn't go down too well.

"My dad is a pretty off-colour character. He wasn't too enthused about me playing him...," the actor confessed.

Once the movie was completed, Shia set up a special screening for his father, but he has yet to ask Jeffrey for his thoughts on the film.

Instead, the 33-year-old chose to monitor his dad's reactions via a webcam as Jeffrey watched the movie, and it appears he was really moved by the personal project.

Shia recalled, "I said, 'Let me just watch you watch it, man,' and it was really emotional."

Honey Boy, directed by Alma Har'el, also stars Noah Jupe and Lucas Hedges as Shia at different stages in his life.