The Beatle, 76, visited his childhood home in Liverpool before leading a singalong with surprised drinkers in a city centre pub.
The skit began with Corden making a phone call in his car, paraphrasing the Beatles’ hit Help! “I’m in Liverpool, and I need your help. Yeah, I need somebody, not just anybody, please, please help me,” he said.
Sir Paul then climbed into the passenger seat and the pair belted out a version of Drive My Car. In a break with Carpool Karaoke tradition, the veteran singer then took the wheel and drove Corden around Liverpool.
During the conversation, Sir Paul revealed he wrote his first song, I Lost My Little Girl, at the age of 14, before treating fans to a snippet.
The pair then drove to Penny Lane, which inspired the song of the same name based on his experiences of growing up in the area, and Sir Paul got out to autograph the famous street sign. Throughout their journey, he pointed out notable landmarks from his youth, including a church where he was once in the choir.
They stopped at the barbershop mentioned in Penny Lane and Sir Paul took selfies with the stunned staff. He recounted the story of how he came to write Let It Be, saying his mother’s dream had inspired the song. The Late Late Show host began to cry and revealed that his grandfather and father once sat him down and played him Let It Be.
From there, they drove to the home where Sir Paul lived as a teenager, in the Allerton area of Liverpool.
Sir Paul demonstrated how his music sounded better in the lavatory and showed where he and John Lennon would write songs together.
The segment ended with Sir Paul treating drinkers in the Philharmonic pub to a surprise gig.
Carpool Karaoke is on Sky One at 10pm tonight