Gwyneth Paltrow kicked Matthew Morrison in the groin when filming Glee.
The actress makes a special appearance this week's episode as substitute teacher Holly Holiday in the musical TV drama and Matthew, who plays Will Schuester, admitted she worried about hurting him as they danced together.
He told website Access Hollywood: "We're doing the Argentine tango, so you're in-between their legs and you're kicking up and stuff."
Pointing to his inner thigh, he added: "So she's kicking in here, and she's like, 'I'm so scared that I'm going to hit your man-love!'
"And I said, 'You know, just go for it.' And she did and she connected a couple of times."
Matthew added that the episode due to air tonight has a steamy theme and will feature Gwyneth's character teaching a class about the birds and the bees.
He added: "The episode is called 'Sexy' and Holly comes back as a sex-ed teacher and we teach the kids about sex through music."
While Gwyneth, 38, is married to Coldplay singer Chris Martin, Matthew is single and admitted he doesn't think he'd make a good boyfriend at present.
He explained: "I'm not dating anyone. I don't feel like I'm in a good place to be a good boyfriend.
"I know how much work it is to be in a relationship and I don't have the time to put in that work right now."