Harry Potter stars Dan Radcliffe, Emma Watson and Rupert Grint will be among the celebs taking part in a Royal birthday celebration for children.
The trio have landed roles in a kids' play to mark the Queen's 80th birthday, held at Buckingham Palace on 25 June.
The Potter clip has already been filmed and will be shown at the palace on a video screen. Dan won't actually be at the palace as he'll be on holiday.
Two thousand children have been given tickets for the star-studded event.
Kelly Osbourne and Jonathan Ross have also been cast in the play, which will be a mixture of live acting and video clips.
The production, called The Queen's Handbag, is part of the Children's Party at the Palace. It will be broadcast on BBC One and the CBBC Channel on the day.
The idea behind the party is to celebrate the success of British children's literature and to encourage kids to read more. The play's storyline is top secret, but organisers say there will be a specially-written scene including Harry and his friends.
Other big names from kids' literature - including Winnie the Pooh, Mary Poppins and Postman Pat - will also be making an appearance.
Although the Queen had her real 80th birthday on 21 April, she also gets an official birthday, on 17 June.
The Queen gets another birthday because it's thought the weather is more likely to be better in June, making outdoor parties that bit more fun.