The stars showed up for Stephen Colbert to bid farewell to his final " The Late Show ."

Stephen Colbert's Late Show farewell was meant to be a cultural moment: a final curtain for one of late night's most recognizable voices.

Though Colbert promised his audience a regular Thursday episode full of joy to end things off, the dominant emotion of his departing show was melancholy – and the style slowly drifted into sci-fi.