"I'll tell you right up front that I'm going to cry," Kimmel said, wiping tears from his eyes. "I'm already crying, which is embarrassing. But I'm not good with this sort of thing and I'm sorry. Especially to those of you who came here to see the show in person, because that's probably not what you came for. But we lost someone that we and I love very much today."
Rickles died Thursday morning at his home in Los Angeles at the age of 90.
"I know it sounds crazy to say he was too young, but he was. Because he was youthful and funny and sharp and generous," an increasingly emotional Kimmel shared. "I was fortunate enough to not only have Don on this show as my guest, but also to become close to him and his wife, Barbara, which was a lot of fun for me."
The 49-year-old talk show host opened up about his past with the beloved comic, and how it took four years to convince him to come on the show.
"We asked him to do the show over and over again, and he didn't know what this [show] was. He knew The Tonight Show and [David] Letterman and that's it. But finally, after we bothered him like 20 times, he gave up and he did the show for my birthday in 2006."
Kimmel said the "exciting" experience of interviewing Rickles made him feel like he "was in some kind of talk show host fantasy camp."
"Sitting behind a desk while Don Rickles made fun of me, [it] was like being a real talk show host for a minute," he shared.
Rickles went on to sit down with Kimmel 17 times after his first appearance, and the pair forged a close friendship.
The comedian was famous for his incredibly acerbic humor and was one of the most celebrated insult comics of all time, beloved for his razor-sharp wit, incredible timing and unparalleled ability to make fun of anything and everything.
Like most comedians who knew Rickles, Kimmel appreciated his sense of humor and knew what an honor it was to be on the receiving end of one of his hilarious insults.
The late night host recalled an occasion when he took Rickles to Mario Batali's Los Angeles restaurant Mozza, and threw him a fun, somewhat lavish party.
"We rented the private room in back," Kimmel shared. "We had food, I invited his friends, it was beautiful. It was very expensive, OK? And I paid for it. At the end of this beautiful meal, he says to me -- I'll never forget it -- he goes, 'I can't believe you took me to a pizza place.'"
Rickles' sense of humor earned him the nickname Mr. Warmth. However, while the moniker was intended to be ironic, Kimmel said that he actually was incredibly warm, caring and sweet.
"He would always ask about my parents, my kids. When my uncle Frank passed away, I called [Don] and asked him to be the guest on that show. Which was a tough show. And he helped all of us through it," Kimmel recalled. "He gave me advice. And good advice, not just the advice people give you to hear themselves giving the advice."
"There will never be another Don Rickles," Kimmel concluded. "He was probably the greatest talk show guest of all time."
Kimmel closed his emotional monologue with a video tribute to the late comic, showing some of Rickles' best moments from the many times he appeared on Jimmy Kimel Live.
Kimmel's first guest of the night was Adam Sandler, and the pair shared some of their memories of the late icon.
"He was just the greatest guy," Sandler said. "I worshiped the guy too."
Sandler recalled a moment, nearly 20 years ago, when he and actor Steve Buscemi were eating at a restaurant in New York and Rickles came up to their table, just to rib them a bit. The experience stuck with Sandler forever.
"[He said], 'So, Happy Gilmore. I watched the whole thing. Wow, amazing how no talent can get you a movie,'" Sandler recalled, laughing. "I was like, 'Yes, yes!' He was the best."
Stephen Colbert also paid tribute to Rickles in his Late Show monologue, sharing a story about the two met backstage at the Emmys.
"While I didn't know Don Rickles, I did have the incredible honor to meet him once," Colbert recalled. "He hugged me and told me I was good. And I felt like a made man."
"We all should [hope] to have his career and be who he was," he added. "Married to his wife, I don't know, 120 years? So God bless you Don Rickles, and thank you."
Late Night host Seth Meyers remembered his first time meeting Rickles as well, back when he was still a cast member on Saturday Night Live.
"A few years ago I was at a party and Don Rickles was there. He was sitting at a table, and he was alone, and I said to myself, 'I will always regret it if I don't go over and say hello to Don Rickles,'" Meyers said.
"I went over and I said, 'Mr. Rickles, I just wanted to say hello, my name is Seth Meyers, I'm on Saturday Night Live.' And he just looked at me and said, 'Oh I'm so sorry to hear Saturday Night Live was cancelled,'" Meyers continued, "and I was like, 'Oh, it wasn't cancelled.' And he just went, 'Ugh, a guy can dream.' … There's nothing better than getting burned by Don Rickles."
Jimmy Fallon also addressed Rickles' death while sitting down on the Tonight Show with former host Jay Leno, who said, "I love that whole generation of comics, Don, and of course Rodney [Dangerfield]... But there's nothing better than comedian funerals, because everyone tells the best jokes."
While The Late Late Show and Conan were both in reruns on Thursday, hosts James Corden and Conan O'Brien paid tribute on social media.
"Don Rickles was one the absolute greats. I feel lucky for the times I was ever in his orbit," Corden wrote. "My thoughts are with his family today."
Don Rickles was one the absolute greats. I feel lucky for the times I was ever in his orbit, my thoughts are with his family today x— James Corden (@JKCorden) April 6, 2017
O'Brien also took to Twitter to share his memories, writing, "I was thrilled to interview/be insulted non-stop by the legendary Don Rickles. I will sorely miss this incredibly funny and lovable man."
I was thrilled to interview/be insulted non-stop by the legendary Don Rickles. I will sorely miss this incredibly funny and lovable man.— Conan O'Brien (@ConanOBrien) April 6, 2017
For more on the life and legacy of stand-up comedy's most beloved insult comic, check out the video below.