Then he paused and spoke slowly about the staff at the Kennedy Center worried about their future. “My eternal thanks for their selfless devotion to the arts,” he said to a roar and a 25-second standing ovation. To which O’Brien joked: “That was plenty.”

But the heart of his speech was an effusive and serious consideration of what Twain stood for. O’Brien said that Twain is “alive, vibrant and vitally relevant today, ” citing his novels as well as his career as a traveling performer. Twain’s enduring power, he argued, stemmed from his core principles, which shaped his comedy.

“First and foremost, Twain hated bullies,” he said, saying he populated his works with them, and made his readers hate them. Twain was allergic to hypocrisy and loathed racism, empathizing with former enslaved people struggling during Reconstruction, immigrant Chinese laborers in California and European Jews fleeing antisemitism.

O’Brien paused, saying that some might be wondering what this has to do with comedy. “It has everything to do with comedy,” he boomed. “I have loved all my life comedy that is self-critical, deflating and dedicated to the proposition that we are all flawed, absurd, and wallowing in the mud together.”

When O’Brien left “The Tonight Show” in 2010, refusing to agree to move its time slot back a half an hour (to make room for Jay Leno), he spoke directly to his audience, with humor and silliness, but also in a new register. He told them to never get cynical, that it leads nowhere.

This tribute to Twain had a similarly earnest tone. There’s always been an ethical underpinning to O’Brien’s buffoonery, a careful commitment to making himself the joke in a way that emphasizes our common humanity. Here he leaned in. When O’Brien described Twain’s faith in travel (quoting him saying it’s “fatal to prejudice, bigotry and narrow-mindedness”), you can detect a serious intent behind his idiot abroad act on the travel show, “Conan O’Brien Must Go.”