The actor, who arrived prepared with a thermometer inside his jacket pocket, requested to test Letterman ahead of their interview, and placed the device inside the host's mouth before carrying on with the question portion of the test.
"Have you traveled abroad lately?" he asked, following up with, "Have you ever kissed a monkey or licked an airport toilet seat?"
When Letterman said "Maybe," Carrey continued with his questions: "Are you now or do you plan to be a member of ISIS?"
After determining Letterman was not sick -- his body temperature was 55, "just like the studio" -- the host asked Carrey if he was "worried about diseases?"
"Once you've done a couple of press tours, you know, you welcome death," Carrey joked. "You do, there's nothing left that's meaningful."
"I've been married a couple of times," he added, "so it takes a lot to scare me, Dave."
Carrey also revisited his Matthew McConaughey impression and got stuck in a claw machine during his visit.
