The two stars dressed in silly disguises and headed to the famed Big Apple locale for a “Musical Photobomb” challenge, dancing and lip-syncing to Bieber’s hit song “What Do You Mean?” behind seemingly unaware parkgoers.
Wearing suits, wigs, sunglasses, and fake mustaches, Fallon, 43, and Bieber, 24, were entirely unrecognizable.
Both looked to be having plenty of fun. Eventually, their playful energy became infections, with kids and other visitors joining them in dance.
By the end of the clip, Fallon and Bieber ripped off their disguises to the thrill of those around them. “Oh my God, Justin!” screamed a sea of teenage girls, who posed with the pop star for selfies.
All was in celebration of The Tonight Show‘s historic visit to Central Park. For the first time ever, the long-running late night staple broadcasted live from a stage in the center of the park.
“It’s a giant deal for us. No late night show has done it,” Fallon told PEOPLE editor-in-chief Jess Cagle in the latest episode of The Jess Cagle Interview.
Fallon also told Cagle about the Bieber segment, which was taped in August. “We have a couple of surprises,” Fallon teased. “We went out and already shot a thing in Central Park with a pal of ours. I don’t want to say his name [but] it rhymes with ‘Justin Greeber.’ Anyway, it’s a really dumb bit and it’s really funny.”
The Saturday Night Live vet also spoke about what he loves about doing The Tonight Show.
“It’s the most fun thing, especially for me,” he said. “I get to interview people every single day. I have different musical guests. We do sketches, we do game-show type of stuff. Every night something different. Just last week we had Paul McCartney do a sketch. I was like, ‘When do you get to see a Beatle do a sketch?’… He calls me Jim, by the way.”
RELATED VIDEO: Jimmy Fallon Previews The Tonight Show Episode in Central Park
Though TV viewers saw Bieber dancing around Central Park on Thursday, the singer was seen that same day walking hand-in-hand with fiancée Hailey Baldwin into a New York courthouse where marriage licenses are issued.
TMZ, which obtained the photo, reported that Baldwin and Bieber appeared to be extremely emotional, with a courthouse insider saying Bieber told Baldwin, “I can’t wait to marry you, baby.”
A source also told TMZ Bieber told a court official, “Thanks for keeping it on the DL.”
However, a friend of Bieber told PEOPLE a wedding is still in the works. “They have hired a wedding planner and have been looking at venues,” ” the friend said. “The plan for now is to have a real wedding.”