Who knew Britney Spears was such a sporty gal?

The X Factor judge goofed around backstage in between the Greensboro auditions for the popular talent show, but once she got on set ... her mood reportedly changed.

The singer, 30, stormed off the set AGAIN during the North Carolina auditions ... after a man, dressed as a woman, sang butchered her song "You Drive Me Crazy." This is the third time that the songstress has stormed off the set.

As for this video ... aside from chomping loudly on that piece of gum, Brit sure sounds amazing.

Can't wait to see the drama when this season's X Factor debuts this September!