Fallon could barely contain his glee as Sir Paul walked on-stage, where he was met with rapturous applause from the studio audience.
"Do you get standing ovations everywhere you go? Starbucks?" Fallon asked.
"Yes," McCartney replied. "Even on the bus."
The "cute Beatle" was recently in Washington to add a Kennedy Center Honor to his nearly endless list of accolades. He admitted that as an Englishman, he wasn't aware of the stature of the award - it's America's most prestigious recognition for lifetime contributions to the performing arts - but that he was floored to receive it.
When asked by Fallon to single out some of his biggest career thrills, though, McCartney pointed to his first visit to the White House last June to receive the Gershwin Award - where he also had his first introduction to President Obama and First Lady Michelle - as a highlight.
"Wait, no one ever asked Paul McCartney to come to the White House?" an incredulous Fallon asked. "What's wrong with America?"
Sir Paul said that playing his famed love ballad "Michelle" in honor of the first lady was a moment he really treasured. At the time, he commented that it might also lead to him being punched out by the president.
He also listed being knighted, playing the Royal Command Performance for the queen, and, of course, appearing on the Ed Sullivan show.
"I remember I was going to play 'Yesterday' solo with an orchestra and the guy who handles the curtains asked me if I was nervous," McCartney said. "I said 'no' and he said 'you should be...there's like 73 million people watching'."
Speaking of "Yesterday," Fallon asked McCartney is he would like to perform the original version of the song, called "Scrambled Eggs." Apparently, to remember the timing of the words, McCartney recalled the phrase, "scrambled eggs."
The duo then hit the stage and broke into it..."Scrambled eggs, oh my baby how I love your legs/but not as much as I love scrambled eggs/oh we should eat some scrambled eggs/waffle fries/oh my darling how I love your thighs/not as much as I love waffle fries/oh have you tried the waffle fries."
Even the drummer for Fallon's house band - ?uestlove of The Roots - could hardly contain his excitement at backing for the legendary musician.
"HOLY ISH......i cant believe we are doing this. #yesterday," he tweeted.
After their rousing duet, the conversation took a more serious tone as Fallon asked about the recent commemoration of Lennon's death, the 30th anniversary of which occurred this past week.
"It was just sort of senseless," McCartney said wistfully, calling Mark David Chapman, Lennon's shooter, the "jerk of all jerks."
"You just thought John would be around forever," he said.
Though the two had a falling out as the Beatles fell apart, McCartney said they had begun to repair their relationship by the time of Lennon's death.
"We would talk about families and making bread," he said, adding that things would have been much more difficult for him had they never reconciled.
He then played a solo version of "Here Today," a song from 1982's Tug of War that was written for Lennon. He called the song a "conversation we never had" and implored people to say things that they need to say to the people they love because you never know when that chance will be gone.Paul and Jimmy sing "Scrambled Eggs" video
