Listen to Miley Cyrus on iHeartRadio | Listen to Britney Spears on iHeartRadio

Britney Spears launched her two year Vegas residency at Planet Hollywood last night, drawing rave reviews and celebulous attendees.

The famous fan who made her presence most known was—no surprises here—Miley Cyrus. During Brit’s performance of “Till the World Ends,” Cyrus started dancing, well, as if the world were ending. Front row, too; isn’t she lucky…

Give it a watch here!