Kelly Osbourne has been on a roll lately insulting not only Christina Aguilera, but Catherine, the Duchess of Cambridge, or "Kate Middleton" too.

"If I am going to be the future bloody Queen of England I'm going to wear that dress once because I'm giving up the rest of my life, all of my privacy, at least I can get a new dress every day," the outspoken Osbourne said on Jay Leno Wednesday night. This was the first time in ten years that Osbourne took the Leno stage.

"In England they are like, look how thrifty she's being, showing the British public that the Royals are in a recession as well."

Middleton is known for her thrifty, yet fashionable style, often "recycling" outfits and wearing them on separate occasions.

On the day of the Tusk Trust's US Patron's Circle in Beverly Hills, Kate donned a pair of sapphire and diamond earrings which match her 19-carat engagement ring. Both the ring and earrings were heirlooms from William's late mother, Princess Diana. Kate however, turned the earrings froms studs to drop earrings. The first time Kate wore them in public was at Wimbledon in June.

Leno asked Osbourne about her undergarments, "How about underpants? Would you throw them away?"

"Well, if I could I would," she replied. She later tweeted, "I had so much fun on @JayLenoTonight thank you for having me!"

On a recent episode of E!'s "Fashion Police" Osbourne was asked to comment on Christina Aguilera's Givenchy dress, but instead Osbourne criticized the singer for her recent weight gain calling Aguilera "fat."

"Maybe she is just becoming the fat b***h she was born to be. I don't know. She was a c**t to me. And she bought my house!" (Aguilera moved into the estate with Jordan Bratman and their son Max in 2008. She told InStyle that she changed the décor by adding "graffiti artwork, Japanese anime and kaleidoscopic rugs.")

"She called me fat for so many years," Osbourne continued, "so you know what? F**k you! You're fat too."

Osbourne has been in the media recently due to the death of one of her best friends, Amy Winehouse, who passed away July 23. On July 23, after hearing the news of Winehouse's untimely death, she tweeted, "i can't even breath right my now im cry,ing so hard i just lost 1 of my best friends. i love you forever Amy & will never forget the real you!" The reality-star was seen at the funeral of Winehouse on July 26 in London. Osbourne hit Twitter to express her sorrows stating, "today was the saddest day of my life!"