AceShowbiz -

It's the end of an era when "The Colbert Report" wrapped up Thursday, December 18. Stephen Colbert welcomed his lifelong friend Grimmy as his final guest and it was revealed that he had accidentally killed the Grim Reaper, meaning he gained immortality.

When the show's back from a commercial break, he bid farewell. "I'm ending 'The Report' and I was gonna say goodbye, but now that I'll live forever, who knows," he said, before launching into a performance of "We'll Meet Again" with Randy Newman on the piano.

He was soon joined by a number of celebrities including Jon Stewart, Bryan Cranston, Willie Nelson, Mandy Patinkin, Cyndi Lauper, Katie Couric, James Franco, Rod Stewart, Jeff Daniels, Andy Cohen, Patrick Stewart, George Lucas, Elijah Wood, Big Bird and Cookie Monster. Vince Gilligan, who's still being held captive in Colbert's basement, Bill Clinton, J.J. Abrams and Smaug the dragon also made cameo.

Later, Colbert was seen on the roof of his studio, contemplating his next move. He met Santa Claus, Abraham Lincoln who has a unicorn horn, and "the man with all the answers" Alex Trebek. He then rode off in the sleigh into the night, but Trebek promised they would "always be there for the American people, whenever they need us the most," which prompted an argument about Trebek's citizenship.

Colbert will return on TV on CBS' "Late Show" after David Letterman resigns next year.