Trouble

Someone at a college gymnasium challenged Rock to a game of one-on-one volleyball. Rock accepted and promptly watched as his opponent rocketed a serve past him that he had no chance to return or so much as touch.
Impressed as he was, Rock could tell that the ball didn't look right. He picked it up to see that it was in fact much smaller than a volleyball. It was no larger than an orange, and it was wrapped in an odd canvas-like cover.
"We can't play with this," Rock said. "I'm going to go check out a real volleyball."
His opponent agreed, and they both began to sprint toward the equipment room on the opposite side of the building. En route, Rock made a right turn across a mat for gymnasts and tried to run between two girls dressed in tights. They failed to move, and Rock ran directly between them as they stood shoulder to shoulder. They both spun around from the contact and fell to the mat.
Almost immediately, Rock knew he was in trouble.
"Shit, man, you can't do that," his volleyball opponent said.
"I know," Rock said. "I don't know what I was thinking."