"I'm just here to irritate him. I was put on this Earth to irritate him," Stallone said with a smile while talking with E! News prior to a screening of the duo's movie Escape Plan at Comic-Con in San Diego, Calif., on Thursday.
He added that both have been known to be practical jokers. A point on which Schwarzenegger definitely concurred.
"That's part of it, to play tricks on each other," said Schwarzenegger. "That's what makes it fun. But when we were on the set and when we were shooting, it was serious business. And you can imagine how competitive Sly is. As you know, we've competed against each other our whole career. I mean, we were trying to outdo each other about who uses the biggest guns, who has the most cut muscles, who has the least amount of body fat, who has the biggest muscles, who kills more people on the screen. It was like a real all-out competition."
Schwarzenegger continued, "It was really great, because we could compete within the movie and the movie really benefits from that because I was really trying to pull out my best performance because I wanted to outdo him. And he pulling out his best performance, so it really helped the movie."
We'll all know for sure when Escape Plan hits theaters on Oct. 18.