Greatest thing ever? Jimmy Fallon slipped into the tightest white pants that he could find during The Tonight Show on Monday, February 15 — and he wasn't alone.

The late-night host, 41, was joined by special guests Christina Aguilera and Will Ferrell for the laugh-out-loud "Tight Pants" skit.

The trio all wore striped shirts with the jeans and rocked blunt haircuts. One by one they walked out on stage, shook their tushes and belted out the catchy "got my tight pants on!" tune as Jennifer Lopez previously did in 2014. (Ferrell also did the dance in 2012.)

"Whoa, slow down there, compadre," Ferrell, 48, said, interrupting Fallon's solo. "You say people are talking about your tight pants down at the penny arcade? Well I find that hard to believe because ever since we moved to this town, everyone we know has been talking about our tight pants."

"Well, that's funny, because yesterday I ran into Mayor Wembley and he declared my pants are the tightest in all the land!" Fallon quipped back.

But the battle got even more ridiculous. Ferrell and Aguilera, 35, said that their newborn child is really the heir of the tight pants throne, which prompted Fallon to drop a crazy bombshell.

"Well ain't that a bag of beans, especially since you and I haven't spoken since that one magical night we shared nine months ago," Fallon said to Aguilera, trying not to break character.

Ferrell replied: "I don't know who you are or what butthole you crawled out of, but this is my woman and that is our baby! And every night he gets swaddled in the tightest of pants."

Watch the hilarious sketch in the video above!

Can't get enough of Us? Sign up now for the Us Weekly newsletter packed with the latest celeb news, hot pics and more!