John Oliver’s not the only talk show host who can drop in on another show unexpectedly. Last night, the great David Letterman made a rare appearance on the Tonight Show right in the middle of ...

David Letterman ... together when Letterman appeared on Strike Force Five, a limited podcast series that Stephen Colbert, Jimmy Fallon, Jimmy Kimmel, Seth Meyers, and John Oliver hosted together ...

David Letterman ... but it was very similar." Letterman's Tonight Show visit was one of two late-night pop-ins Monday. Former Daily Show correspondent John Oliver returned to that show's set ...