Stars react to Prince William and Kate's baby news

Prince William and his wife, Kate, Duchess of Cambridge, walk together during the opening of the Football Association's National Fooball Center at St. George's Park in Burton upon Trent, England.

Prince William and Kate announced Monday that they're going to be parents, and reactions have begun pouring in.

Kate Middleton, #Kate and #royalbaby quickly became top trends on Twitter after St. James' Palace revealed news of the Duchess of Cambridge's pregnancy, and well-wishes have since come from celebrities and even Britain's prime minister.

Here's what some of them had to say: