“The Late Show With Stephen Colbert” signed off with a little help from the host’s friends.

“The Late Show with Stephen Colbert ” came to a climactic and possibly interdimensional end on Thursday night as the show’s final guest led a rousing sing-along to an almost too-fitting song.

Sir Paul returned to Ed Sullivan Theater, as it was renamed in 1967, to sit for an interview with Colbert on the host's final broadcast, and then performed The Beatles' " Hello Goodbye ," with Colbert...