George Lucas, Sir Patrick Stewart, Neil DeGrasse Tyson, Elijah Wood, J.J. Abrams and Smaug represented sf and fantasy in the musical finale of The Colbert Report , coming to an end so its host can replace Letterman on CBS.
An army of celebrities emerged from the wings to join Colbert in singing “We’ll Meet Again,” beginning with his Comedy Central colleague Jon Stewart, then Willie Nelson, Kareem Abdul-Jabbar, Doris Kearns Goodwin, Henry Kissinger and dozens of others — the full array of cameo appearances is listed here.

James Franco, Andy Cohen, Sir Patrick Stewart, Elijah Wood, Henry Kissinger, Mike Huckabee, Bob Costas, Tim Meadows.
Others of genre interest for one reason or another, scientist Francis Collins, economist Paul Krugman, an astronaut on the International Space Station and Marvel Comics’ Joe Quesada.
Even “We’ll Meet Again” is an sf reference — it’s the song played at the end of Dr. Strangelove while the nukes are going off.