TORONTO – Dwayne Johnson was given an unusual order for his latest role: The muscular actor and pro wrestler was asked to gain weight and get bigger.

That was just part of the transformation into former mixed-martial arts champion Mark Kerr in director Benny Safdie's sports drama "The Smashing Machine" (in theaters Oct. 3). Johnson's all-in portrayal is not only earning a ton of Oscar buzz, it also fooled the real Kerr.

The first time he saw Johnson in full facial prosthetics – including blunt trauma-induced "cauliflower ears" – Kerr turned around and "he’s standing right behind me and it’s me!" Kerr said in a post-premiere Q&A at Toronto Film Festival. "All I could do was cuss at him. It was so surreal."

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"Smashing Machine" takes place in Kerr's life between 1997 and 2000, where the MMA fighter rose to prominence but also had to fight demons including drug addiction. He has girlfriend Dawn (Emily Blunt) by his side, yet they also weather severe ups and downs when it comes to their personal life and his career.