Len Lesser, the 88-year-old character actor best known for playing Uncle Leo on Seinfeld, passed away Wednesday in Burbank, Calif., from cancer-related pneumonia, his family said in a statement. The New York-born World War II veteran had roles in such films as Outlaw Josey Wales, Birdman of Alcatraz, and Papillon, and appeared in a wide variety of television shows including Get Smart, The Munsters, The Monkees, The Rockford Files, and ER. He’s most recognized for the 15 episodes that he spent in the 1990s on Seinfeld as Jerry’s arm-grabbing, close-talking, “Jerry! Hello!”-exclaiming uncle.

UPDATE: Seinfeld co-creator/star Jerry Seinfeld paid tribute to Lesser in a statement: “Len was one of our favorites. We always loved having him on the show. I’ll never forget when Uncle Leo was in prison and tattooed ‘Jerry Hello’ on his knuckles. He was a very sweet guy.” On his Twitter page, Seinfeld star Alexander remembered: “Len was a tremendous guy. He was a smart actor/comedian who knew exactly what he was doing in the creation of Uncle Leo. I enjoyed many wonderful conversations with Len who was so openly grateful to be part of our show and so humble about his stunning contribution to it. I am so happy to have known him and my sympathies go to his family. But his was a fun life and he leaves many fans behind and many who will be enjoying his work for years to come. ‘Hellooo’ Uncle Leo. And goodbye. Sleep well. Much love.”

Lesser also guest-starred in multiple episodes of Everybody Loves Raymond as a friend of Frank (Peter Boyle). His last TV credit was a 2009 Castle episode.