Simon Cowell, Sharon Osbourne and Louis Walsh reunite at London nightclub

On Feb. 15, 2013, Simon Cowell, Sharon Osbourne and Louis Walsh — the original judges on "The X Factor" U.K. — had a very public reunion when they hung out together at the Arts Club in London. The Sun published paparazzi photos of the trio leaving the club. The reunion has sparked more speculation that Osbourne may go back to "The X Factor" U.K. judging panel.

Singer/reality TV star Sinitta (who is one of Cowell's ex-girlfriends) was also partying with Cowell, Osbourne and Walsh at the Arts Club. Sinitta has been an on-again/off-again guest mentor on "The X Factor" U.K., and she remains friendly with Cowell.

In 2012, Osbourne was a guest mentor assisting Walsh on "The X Factor" U.K.

It has not been officially announced which judges will be on "The X Factor" U.K. in 2013. Representatives for "The X Factor" U.K. are currently refusing to comment on any changes to the show that will be made in 2013.

In August 2012, Sharon Osbourne fueled speculation that she might return to "The X Factor" U.K. when she tweeted that she wanted to go back to being a judge on the show in 2013. She posted this statement on Twitter not long after she announced that she was ending her five-year stint as a judge on "America's Got Talent."

British tabloids have been publishing reports that Sharon Osbourne has been in "secret" talks to return to "The X Factor" U.K. in 2013. The tabloids have speculated that Osbourne would replace "X Factor" U.K. judge Tulisa Contostavlos. Meanwhile, Contostavlos tweeted an adamant denial on Jan. 13, 2013.

Cowell, Osbourne and Walsh were the original judges of the show when it launched in 2004. This trio lineup remained until 2007, when Dannii Minogue joined "The X Factor" U.K. as a fourth judge. Minogue and Osbourne famously fueded because they had personality conflicts, and Osbourne quit the show at the end of 2007 because she said she no longer wanted to work with Minogue.

Osbourne was replaced by Cheryl Cole in 2008. Cole, Cowell and Minogue were judges on the show until 2010. Cowell and Cole quit the show to become judges on "The X Factor" U.S. in 2011, but Cole was notoriously fired after less than a month on the job. Minogue either quit or was fired from "The X Factor" U.K., depending on whom you believe.

In May 2011, with Walsh the only remaining original judge on "The X Factor" U.K., Gary Barlow replaced Cowell, Contostavlos replaced Cole, and Kelly Rowland replaced Minogue.

Rowland parted ways with "The X Factor" U.K. in April 2012, because she was reportedly unable to reach an agreement with the show over her salary and time commitment. After Minogue told the media that she turned down an offer to replace Rowland on "The X Factor" U.K., Nicole Scherzinger replaced Rowland in June 2012.

"The X Factor" creator/executive producer Cowell has already stated that he will not go back to being a judge on "The X Factor" U.K. as long as he is a judge on "The X Factor" U.S., since both shows do their live shows during the same months.

As of now, Cowell is the only judge confirmed for "The X Factor" U.S. in 2013. The replacements for Britney Spears and L.A. Reid have not been found. And it has not yet been announced yet if Demi Lovato will continue to be a judge on the show. Lovato has said in recent interviews that she doesn't know if she will be still be an "X Factor" judge, but that she would say yes if she is asked to return to the show.