The Fighter star asked the former wrestler to stop by his trailer and say hi to his sons, who are big fans, but he never thought his kid's painful penchant for greeting men would apply to the three year old's hero.
Wahlberg recalls, "They're in the trailer, he gives my one son a high five and then the next one he goes to give him a high five and my son... (punched him) right in the nuts.
"I'm like, 'What are you doing, dude?' And he (Johnson) looks at me like I made him do it or something. I thought he was gonna try to, like, pick me up and slam me."