The blonde TV presenter, 32, tweeted a picture of herself dressed in an American flag-themed cheerleading outfit and shaking a pair of pom poms on Thursday (12 September).
But before you start thinking Holly's heading back to school Never Been Kissed-style, it's actually a costume from tonight's Celebrity Juice.
Holly didn't give any information on what the sketch is about, only tweeting: "Shaking my pom poms, tonight on @CelebJuice ITV2 10pm!"
Earlier in the day, her fellow Celebrity Juice team leader Fearne Cotton shared a picture of herself on set.
We're guessing there is some sort of stereotypical geek/popular girl theme to this sketch?!
Fearne has just returned to Celebrity Juice from maternity leave, following the birth of her first child, Rex, in February.
Holly, meanwhile, is about to get even busier, juggling her This Morning and Celebrity Juice roles with Surprise Surprise, which returns Sunday, 15 September on ITV.
She recently told What's On TV that she understood why the series – originally hosted by Cilla Black – had been so successful for such a long time.
"I think it has such history and viewers also have such fond memories of watching it the first time round with Cilla - the fact that it ran for so long shows how popular it was, they took it into their hearts. I think even if it was a brand-new format people would take it into their hearts because of the nature of the show. You can't help but be moved by the stories."
Celebrity Juice continues tonight on ITV2.