Ashton Kutcher was grumpy on the Jobs set because he ate only grapes.
The 35-year-old actor adopted Steve Jobs' fruitarian diet to get into character as the late Apple creator for his new biopic, but his co-stars soon felt the negative effects of the drastic regime.
Josh Gad, who plays Jobs' business partner, Steve Wozniak, joked, "He went on a fruitarian diet. I went on a cheeseburger diet. The toll was a lot harder on him than it was on me . . . He was grumpy the first couple of days because he was only eating grapes."
However, the bad mood clearly didn't impact Ashton's performance as Josh added he was "probably the best scene partner I have ever had".
The Two and a Half Men actor recently admitted he was rushed to hospital with severe pancreatic pain after weeks of following the same diet as the computer whizz, who passed away from a rare form of pancreatic cancer in October 2011.
The star also brushed up on Jobs' Zen Buddhist philosophy and sought the help of an acting coach to help him portray Jobs and all his quirks.
Ashton said, "The most valuable thing I did was I willing to admit I probably didn't know how to do this. I found an acting coach that helped me do it.
"Sometimes when you have the humility to admit you don't know what you are doing, you can find somebody to teach you that maybe you actually did."