'X Factor' Top 3 Revealed, Emblem3 Elimination Shocks Britney Spears (WATCH VIDEO)

A frontrunner for "The X Factor" was shocklingly eliminated from the Top 4 acts on Thursday, Dec. 13.

One of Simon Cowell's groups was sent home, despite becoming a favorite among the judges, in a decision solely based on audience votes.

The show began with Carly Rose Sonenclar, Tate Stevens, Emblem3 and Fifth Harmony all sharing the stage to perform the Diddy-Dirty Money song "Coming Home." The contestants had already wowed fans with solo performances on Wed, Dec. 12.

"The X Factor" co-hosts Mario Lopez and Khloe Kardashian made a surprise announcement after the set: they shared that Cowell's girl group Fifth Harmony took the first spot in the finals.

"This is absolutely phenomenal!" said Fifth Harmony's Ally Brooke.

"I believe in miracles. I could not be happier," said a proud Cowell. L.A. agreed, adding, "I'm very shocked. You said last night anything can happen and it just did."

Britney Spears' reaction to the news, however, stole the spotlight. Her face appeared horrified and it was apparent that she blatantly disagreed with the viewers who voted Fifth Harmony into the top three.

"I was a little disappointed. I thought it was going to be the other way around with the groups," Spears said.

Later, Spears' facial expression became a trending topic on Twitter- the hashtag "#BritneySurprisedFace" went viral even before the episode ended. The second act America chose was Tate Stevens and the 37-year-old's reaction was tame compared to the other acts. He calmly said, "This is amazing."

"I'm very, very proud. I am a Tate Stevens fan," said his mentor Reid, who then admitted he was never a country music fan.

The last two acts anxiously awaiting their fates on stage were Spears' act Sonenclar and Cowell's group Emblem3. When Lopez announced Sonenclar was moving on to the next round, the 13-year-old said a "thank you" speech that praised the defeated boy band.

"I don't even know what to say. Thank you so much for voting and Emblem3. I know you're going to go so far and I'm going to buy your album," she told the trio.

"It's all good. We love you and we're going to continue to do music," said Emblem3's Wes Stromberg.

The finalists in "The X Factor" season two are Fifth Harmony, Stevens and Sonenclar. The toTop 3 will return for the season two finals next week for a chance to dethrone last year's champion, Melanie Amaro, win a $5 million recording contract and appear in their own Pepsi commercial that will air during the 2013 Grammy Awards. The finals will air on Wednesday, Dec. 19 at 8/7 p.m. C on FOX.

Watch the video below featuring Spears' surprise face that ended up becomiing a trending topic on Twitter.