Mark Ruffalo has revealed his four-year-old daughter Odette was terrified of his Hulk alter-ego.
But the 44-year-old, who plays the latest incarnation of the mean, green giant in Joss Whedon's Avengers Assemble, admitted his ten-year-old son Keen had the opposite reaction.
"It totally freaked out my daughter when I turned into the Hulk," he said.
"She jumped on my lap and said, 'Why do you want to kill that girl, Papa?' And my son was so happy. They love the movie."
He added: "You know, the Hulk's kind of scary - you see your dad turn into the Hulk and it's scary. He looks so much like Banner at that moment when he turns the first time so it kind of freaked them out. They had never seen me like that."
Mark enjoyed "breaking out" the smashing machine.
"It was a blast. I was excited about the idea of being able to play both Banner and the Hulk. That was something that really turned me on in doing this," he continued.
"I watched the other movies and when it got to the Hulk section, it always seemed like he wasn't human. So when I spoke to Joss, I really wanted to do the motion capture and refine all the facial movements and physicalisation. It was a three-step process: we did it before we shot the movie, while we were shooting and after we shot the movie."
Robert Downey Jr, Scarlett Johansson and Tom Hiddleston also star in Avengers Assemble, which opens on April 26.