Other Minor Characters
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Seinfeld Supporting Cast
In addition to Seinfeld’s main characters, the supporting cast was equally sparkling and added a great dynamic to the show and the storyline. Each brought a wealth of quirk and comedy to the show, and added a new level of dimension for the main character they supported.
Frank Costanza
Frank Costanza (played by Jerry Stiller) is George Costanza’s father on Seinfeld. As an Italian native, born in Tuscany, he brought a wealth of culture (perhaps culture shock) to the show and added a dimension to 
George’s character that was absolutely necessary to understand George as the person he had become—neurotic, paranoid, and irascible, just like his father.
Frank Costanza was not necessarily a “warm and fuzzy” father. To the point, brisk, and sometimes abrasive, he dominated George and had a knack for guilt trips and eccentric likes and dislikes.
Some fun facts about Frank Costanza include his fluency in Korean, his love for food, and his work in as an Army cook. He’s also a fan of Latin American vinyl and he created the first man-bra for Kramer in “The Doorman.”
Uncle Leo
Uncle Leo (played by Len Lesser) is Jerry’s uncle. He’s a slight nut case and very unconventional —perhaps with a chip on his shoulder as well. His catchphrase in the show “Jerry! Hello!” is his signature greeting. He’s very fond of Jerry, in fact tattooing “Hello” and “Jerry” on the fingers of each hand. Uncle Leo is a sensitive soul—when Jerry avoided him on the street, he was deeply offended and notified Jerry’s mother to complain.
Fun facts about Uncle Leo include his obsession over anti-Semitism, his constant insecurity, and his worry that everyone is out to get him. He’s retired and constantly speaks about his successful son, Jeffery, in nearly every episode he’s featured in.
Susan Ross
Susan Ross is George Costanza’s since-deceased fiancée. We get to learn about Susan in Season 7’s 
premier episode, “The Engagement.” Even though George is partially in love, he still proposes to her but later gets nervous about his current commitment. Instead of simply telling the truth, George creates elaborate schemes to try to persuade Susan to break it off. Unfortunately, none of George’s erratic behaviors scare Susan off.
Finally, in a twist of fate, Susan dies from ingesting toxic glue from the cheap wedding invitations that George insisted upon. Later, Susan’s parents set up a memorial where George becomes head of council—to his dismay. George becomes immensely sad after realizing how much money he could have had in bereavement inheritance should he have married Susan. At the end of the misadventure, a court case reveals George’s responsibility in selecting the dreaded toxic wedding invitations.
Fun facts about Susan Ross include her lesbianism (which “didn’t take” according to George), her uptightness (she snubbed Jerry and Elaine in a movie theater when they wouldn’t pipe down), and her denial for reality.