WATCH: Jennifer Lopez Scares The "Tight Pants" Off Jimmy Fallon

Jennifer Lopez and Jimmy Fallon in their tight white pants on The Tonight Show

Don't mess with Jenny.

Jennifer Lopez scared the "tight pants" off Jimmy Fallon on Monday night's episode of The Tonight Show. Both Lopez, 44, and Fallon, 39, took to the stage in matching outfits -- much to the comic's dismay.

Before J.Lo appeared on stage, Fallon sang, "I'm the only one who's got my tights/ I've got my tight pants/ I've got my tight pants on/ No one else around is wearing tight pants."

Things got heated when Fallon realized Lopez was bumming his style. The two duked it out on stage, until Jenny from the Block lost it on the host: "Listen up, you little b*tch. You better hide your kid, hide your kids, because I will cut you!" she yelled.

"Don't make me take off my hoops!" she threatened, as she pulled off her gold earrings. 

Fallon backed off (we can't blame him!) as Lopez said, "What I'm trying to say is get lost, applesauce. I'm the only one who can wear tight pants in this town. You feel me? Don't rattle the cage. We cool-o, papi chulo?"

Too funny! Watch below: