A careful blend of sincerity and insults made for a raucous tribute to retired late-night TV host David Letterman at Washington, D.C.’s John F. Kennedy Center on Sunday night, when the company celebrated the 20th anniversary of the Mark Twain Prize, its annual award for American humor. The ceremony, taped to air Nov. 20 on PBS stations, featured a parade of the honoree’s comedic chums for a night of impertinent reflection about their pal, who looked on — and frequently shouted back — from his box seat in the center’s Concert Hall surrounded by family.

The appropriate mood was established with an opening segment that featured one grand piano and two characters — Steve Martin at the keyboard and Martin Short lounging on top for a eulogy of nonsensical chatter. “What better time than to celebrate life than by looking like a confederate war general,” said Martin. The bit was followed by the usual opening salvo of video clips from Letterman shows on NBC and CBS. (Stupid pet tricks kicked things off.)

Jokes about Donald Trump were kept to a minimum, at least until Jimmy Kimmel walked on stage. “Everything was fine until you went off the air and left us with an orange stepfather,” he remarked. The comment was followed by a heartfelt look at Letterman’s serious side — especially his show that followed the Sept. 11 attacks, when Letterman opened the episode cold to help reassure the nation. “You led us with your humor and your empathy,” said Kimmel.

Others on hand included U.S. Senator Al Franken, the former “Saturday Night Live” stalwart who slipped back into comic mode to praise Letterman for such groundbreaking bits as the “monkey cam.” Franken also touched on the sobering issue of climate change, and his collaboration with Letterman to promote that topic in internet videos. There was also a video tribute from former First Lady Michelle Obama, who noted Letterman’s curious side and his reminders not to take life too seriously.

In a refreshing departure from previous Twain ceremonies, a bit of sketch comedy was inserted into the string of stand-up roasts. It included a video skit from former “SNL” alums Fred Armisen and Bill Hader, who played a pair of boyhood yokels from Indiana reminiscing about their buddy.

Others on hand included comics Norm Macdonald, John Mulaney, Amy Schumer, and Jimmy Walker; band leader Paul Shaffer backed by the World’s Most Dangerous Band; and singer Eddie Vedder. Also included was an off-kilter cameo by Letterman’s psychiatrist, Clarice Kestenbaum. “If you ever need a solid 45-minute nap, drop in,” she said before reflecting on Letterman. “He’s crazy. Not Trump crazy, but who knows?” she said.

Another highlight was the introduction of last year’s Twain Prize winner, comic Bill Murray, conducted with Elizabethan fanfare as Murray sauntered down the aisle clad as King Henry VIII. “What a reign it has been,” he confided to the audience before ordering a sandwich for himself and food for the honoree’s box.

For the event’s 20th year, a tribute sequence tipped its hat to past recipients with brief clips of their acceptance speeches or other material. Kennedy Center Chairman David Rubenstein introduced the evening by stressing the importance of the event as a fundraiser for the institution. He said this year’s show raised a record $2.2 million.

In his own acceptance of the Twain Prize, a miniature bust of the humorist, Letterman delivered a blend of levity and sincerity. “Is it wrong that I kinda wish that I would have received this award posthumously?” he asked.

Letterman followed with his own tribute to the artists who had gathered for the evening of fun, praising their talents and in some cases their contributions to his own career. He noted how a kid from Indiana arrived in California and got a job at the Comedy Store where he learned how to be a stand-up comedian. “I went there May 1975, and in April 1978 I was a guest on the ‘Tonight Show.’ Here I am receiving this award, and I ask myself how did this happen?”

“It wasn’t because of me,” he continued. “It was because of perhaps thousands of people who helped me. They all helped me,” he said, citing actor-comedian Walker, who gave him his first job, as one example. Letterman ended with a plea for people to seek opportunities to assist others in life. “We all have to help each other or else nothing will happen. If you help someone in any way, big or small, you will feel good about yourself.”