Then you're going to LIVE for this video!!!
She's gone undercover -- and she OWNS it!
Ch-ch-check out the video for Birthday here (above)!
And the Most HIGHLARIOUS Costume Award goes to…
Deryck Whibley and Ari Cooper!!!
Deryck really knows how to work a frown! Ha
Think any other celebrity's Halloween costume will be able to beat the hilarity here??