The Tommorrowland star's final Late Show appearance with Letterman took a serious turn when he commended the host for his time on the air.
"What you've meant to us with so many of the laughs, walking us through times that we didn't know what to do, like 911 when we weren't sure when we could laugh again," Clooney said. "You belong to us through the ages."
Lightening up the mood, Letterman then took a selfie with the star. "Look it! It's George and his grandfather," the host said of the selfie.