"It's Britney B*tch" and she's definitely back with a two-year residency show called "Britney: Piece of Me" at Planet Hollywood in the Axis Theater.

Billboard.com reviewed the opening night last Friday, December 27, 2013 as an of the high energy, non-stop hit bonanza which left most show goers in awe. The show featured 24 songs over 90 minutes.

However, it seems like not all those in attendance were impressed by Brit-Brit. Tmz.com writes "Britney blew everyone away during her Vegas debut last night... everyone, but Katy Perry" and posted a video of a less than enthused Ms. Perry. The singer looked like she'd prefer to be anywhere else instead of at Britney Spears' concert.

Her demeanor was much more noticeable given that the "Fireworks" singer was seated right beside a spirited Selena Gomez and Miley Cyrus who could not stay in their seats long enough to catch a breath. Dailymail.com reported the 29-year old singer sat in her seat most of the time, hardly moving and at one point checked her phone and held a conversation with a friend.

Katy even tweeted, "Soy excited to see @britneyspears baby bottle pop it off tonight at her grand opening @phvegas! We are coming in full lewks to support!" before the show. It's a wonder why the Pop performer was such a party-pooper during a spirited event. Could it be that there's trouble in Paradise in her relationship with John Mayer?

Click here to view the video of Katy Perry during Britney's debut night.

During the same performance, Britney Spears was caught in the middle of another lip-synching controversy as on lookers say she was miming during her concern. Msn.com quoted the singer's manager Larry Rudolph, "There might be some numbers where she's full out dancing with a [vocal] track underneath her, but there won't be any lip-syncing across the board."

However, critics say it was apparently lip-synced while actual live vocals were minimal during the show. Los Angeles times reported, "The singer appeared to be lip-syncing for the majority of her performance...That went for high-energy dance numbers such as 'Womanizer' as well as slower-paced ballads like 'Perfume,' for which Spears took a seat onstage."

Britney Spears will be receiving an estimated $16 million per year for a total of 96 concerts within two years.