The Hot N Cold singer held the bash at The Sunset Beach nightspot in Los Angeles and guests at the party who had been told to wear white - were left covered head-to-toe in paint.
One said: "They got a little crazy with the paint. I wasn't expecting it but everyone got painted - even Taylor Swift!"
The birthday girl arrived at the party which had Oompah Loompahs running around and a huge variety of candy and chocolate inspired by the sweet maker’s workshop from Roald Dahl's classic tale, Charlie and the Chocolate Factory - and guests say they couldn’t keep their hands off each other.
One reveller said: "They were totally loved up! Katy was having a ball and Russell was catering to her every whim. At one point he was down on his knees bowing and offering her a huge swirly lollipop. She grabbed it from his hands and pretended to knight him with it."
Celebrity blogger Perez Hilton was among the guests and insists Katy’s hospitality didn’t disappoint.
He said: Dinner included lots of yumminess, especially some deelish yellow and green mashed potatoes - and there were so many sweets downstairs for dessert that we’re surprised we didn’t go into a food coma.
Click here for more Entertainment News
