Liz Sheridan, the actor best know for her role as Jerry Seinfeld’s mother Helen in the classic sitcom “Seinfeld,” died on Friday, a representative confirmed to Variety. She was 93.

Seinfeld reacted to the news on Twitter, writing, “Liz was always the sweetest, nicest TV mom a son could wish for. Every time she came on our show it was the coziest feeling for me. So lucky to have known her.”

Born in 1929, Sheridan got her start as a nightclub act, earning a living by dancing and playing in both New York City and Caribbean clubs. During her time as a nightclub act, she had a romantic relationship with James Dean pre-fame and would write about their relationship in her memoir “Dizzy & Jimmy,” which was published in 2000. She would meet her husband, jazz musician Dale Wales, while performing at a Puerto Rican club.

In the ’70s, Sheridan began appearing extensively in Broadway productions, from plays like “Best Friend” in 1976 and “Once a Catholic” in 1979 to musicals such as “Frank Merriwell” in 1971 and “Something’s Afoot” in 1976. In 1977, she co-starred with a young Meryl Streep and Christopher Lloyd in a production of the German crime musical “Happy End.”

Sheridan’s first screen credit is a 1977 episode of the crime drama “Kojack,” playing a minor character. In the ’80s, she moved to Los Angeles and developed a thriving career as a character actor on TV. For the next two decades, she had numerous guest spots on popular shows such as “Archie Bunker’s Place,” “St. Elsewhere,” “One Day At A Time,” “Three’s a Crowd,” “Newhart,” “Moonlighting,” “The A-Team,” “Who’s the Boss,” “Hill Street Blues,” “Remington Steele,” “Cagney & Lacey,” “Family Ties,” “Murder, She Wrote,” “Melrose Place,” “Blossom” and “Sliders.”

In 1986, she scored her first recurring role in the NBC family sitcom “ALF,” playing the nosy, gossiping Raquel Ochmonek. Raquel appeared in the show’s pilot episode and was one of the most frequent recurring characters in the show, spying on the central Tanner family and nearly discovering the existence of the titular alien they were hiding.

Outside of the core four main characters, Sheridan was the only cast member of “Seinfeld” who appeared in all nine seasons of the show’s run, making her first appearance in the second episode of the show in 1990. She would make 21 appearances in the series, acting opposite Barney Martin, who played Jerry’s father, Morty. Sheridan portrayed Helen as a voice of reason compared to the more neurotic Jerry and Morty, albeit one who was deeply overprotective of her only son.

After “Seinfeld” ended, Sheridan would frequently perform a one-woman stage show, “Mrs. Seinfeld Sings.” Other notable credits include a voice role in the 1994 animated show “Life With Louie” and film appearances in “School Spirit,” “Who’s That Girl,” “Wedding Bell Blues” and “Play That Game.” Her final film role was in the 2010 movie “Trim.”

The news of Sheridan’s death comes just weeks after the death of her “Seinfeld” co-star, Estelle Harris. Like Sheridan, Harris played the parent of one of the main characters, in her case George Costanza (Jason Alexander). The two appeared in four episodes of the show together, including the final episode, which aired in 1998.

Sheridan is survived by her daughter.