Britney Spears is an Alien from Mars, as shown In her music video for "Oops I did it again". She started her career when she was born as Kim Kardashian's sister. Baby Sun, their father, blackmailed the Mickey Mouse club into letting them in, but Kim didn't make the cut. Soon after Britney did that, she flew to Mars, filming her music with martians. She eventually came down to earth and settled in Canada, where she lurks in the jungles.
Since Britney lives in the wilds of Canada, she normally feeds on whatever is there. Derpcats, UNICEF workers, magical pickles, etc. are her normal diet.