Jennifer Lopez Squeezes Into 'Tight Pants' With Jimmy Fallon (Video)

"The Tonight Show" host brought back his popular sketch with J.Lo joining in the fun and dance, while Lena Dunham lent Sia a hand performing "Chandelier" over on "Late Night."

Jimmy Fallon brought back his "Tight Pants" sketch on Monday night, this time with Jennifer Lopez joining in on the fun.

Both sang about their white skinnies, competing for tight pants supremacy. "Listen up you little b---," Lopez playfully confronted Fallon, both wearing bowl-cut wigs, ridiculously colorful shirts and skin-tight white pants.

Things got real when J. Lo schooled Fallon on the merits of her winning pair of "tight pants." Of course, the skit wouldn't be complete without a cheeky closeup shot on Lopez's behind.

On Seth Meyer's Late Night, Lena Dunham gave her interpretation of Sia's "Chandelier," complete with blonde-wigged head shaking and prancing in a white trouser suit.

During his opening monologue, Meyers talked about California Chrome failing to win the Triple Crown on Saturday, but reasoned that despite the loss in the Belmont "it is just another Monday for California Chrome, in fact he probably doesn't even know we have days of the week."

The host went on to wish "our good friend" Tracy Morgan a speedy recovery after being involved in a serious car crash. "We love you Tracy and we hope you get well soon."

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Channing Tatum and Jonah Hill continued their press tour for 22 Jump Street by visiting Conan O'Brien and telling the host about their raunchy bet over how much the comedy sequel would make in its opening weekend. "There is a key piece of fabric in the story," revealed Hill. Taum won the bet -- and Hill's "gambling career came to an abrupt end."

On CBS, David Letterman welcomed Kelsey Grammer, who will appear in three of the summer's big blockbusters. "I did a Transformers thing in which I am the bad guy, which is a lot of fun, and I'm in Sylvester Stallone's movie, The Expendables 3," he said, along with making a cameo in X-Men: Days of Future Past.

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The Frasier star also revealed his biggest fan, who even got his face tattooed on her arm with his signature under it.