The surprise was part of a recurring segment, "Elevator Surprise," on Fallon's show. Visitors taking a tour of 30 Rock, NBC's headquarters, were led onto an elevator. Instead of the elevator doors opening on the intended floor, the doors open on the wrong floor to reveal a celebrity waiting to surprise them.
Before guests arrived, McCartney and Fallon sat in velvet wingback chairs, holding up newspapers to obscure their faces.
When the first elevator arrived, Fallon lowered his newspaper first and the crowd gave a heartfelt but lackluster cheer. Moments later, McCartney lowered his paper and the crowd let out a loud scream of surprise. One woman placed her hands on both sides of her face and shrieked.
The next group to stop stood in pure shock, with one visitor shouting, "What?" A star-struck fan standing at the front of the elevator then began to walk onto the floor but was quickly pulled back onto the elevator.
In the third group, Fallon asks the elevator riders if they want to see a magic trick and holds up a scarf, only to drop is seconds later, revealing the famous Beatle.
"I thought when I was little I thought I was going to marry Paul McCartney. That is the closest I ever got and I am thrilled," one McCartney super-fan said.
For another group, McCartney and Fallon play a round of table tennis when the doors open. A fan can be heard shouting, "No way!" McCartney then turns and shouts back, "Yes way," before the doors close again.
McCartney even grabbed a guitar and sang "Drive My Car," but when the elevator doors opened, no one was on the lift.
McCartney recently released a new album called "Egypt Station." During his appearance on Fallon's program, he called the songwriting process cathartic.
"The good thing about songs is if you are in a bad mood, it is a great thing to do," McCartney said. "It's like a therapy for yourself. If you are feeling bad, you can go off somewhere with a guitar and start kind of telling your troubles to the guitar and you kind of work out your problem. And, normally, you get a bit optimistic toward the end of it and then suddenly you have a song. "