Britney Spears made her Las Vegas debut last night at Planet Hollywood, and she had a very famous fan sitting front now:
The 21-year old was totally into a Britney track at one point, mouthing the lyrics and dancing along to the beat.
Watch Cyrus shake what her mama gave her while Spears struts down the stage now:
As for how Britney herself did? Check out these videos from the concert: