Jimmy Fallon's Craziest "Tonight Show" Moments

This is Melissa McCarthy like we've never seen her!

"The Boss" star pulled out all the stops on "The Tonight Show" on Monday night, taking on host Jimmy Fallon in a hilarious Lip Sync Battle.

The comedian started the competition with a funny rendition of the classic song, "Brand New Key." But, McCarthy quickly showed him that she was in it to win it by slaying her performance of DMX's "X Gon' Give It to Ya."

Wearing black leather leggings, a black top, matching sneakers and a baseball hat, the "Gilmore Girls" alum perfectly recited the lyrics while showing off some impressive dance moves!

Fallon knew he needed to step it up, so he tried his best to one-up Melissa with Zayn Malik's "Pillowtalk," complete with his own pillow on the stage.

While he definitely earned some points with the crowd, McCarthy brought it home with "Colors of the Wind" from "Pocahontas."

Throwing on a pair of safety goggles, the actress ended up covered in leaves, feathers, trash and even birds!

"Melissa McCarthy, you’re Lip Sync Battle champion!" the late-night host declared.

Check out the clip to see them in action!