The song that Stephen Colbert and his assembled multitude sang on the final episode of “The Colbert Report” was “We’ll Meet Again,” written in 1939 by Ross Parker and Hughie Charles, made famous by Dame Vera Lynn in the 1943 movie of the same name. It has also been used many other times in pop culture, from “Dr. Strangelove” to The Muppets to “True Blood.” Here’s a list of all the celebs who turned up to wing it with Colbert.