She passed away today in New York City, where she was famous for playing Jerry's mother on Seinfeld, who later appeared on several shows.
Amanda Hendon, a long-time friend and rep, told Deadline that Sheridan died overnight in her sleep due to natural illness.
When she was introduced as the grumpy neighbor Raquel Ochmonek on NBC's ALF, She appeared in about three dozen episodes from 1986 to 1990. Soon after, Helen Seinfeld became the mother of Jerry Seinfeld, who performed in more than 20 episodes, including from Episode 2 The Stakeout at the beginning of Season 2 to the 1998 finale.
Sheridan provided the voice of Mrs. Stillman during Seinfeld's 1994-1998 animated sitcom Life with Louie, with Louie Anderson.
In the 1977 musical Happy End, she appeared on Broadway, including opposite Christopher Lloyd and a young Meryl Streep.
Sheridan later wrote a book about her 1950s romantic relationship with James Dean. Published in 2000, Dizzy and Jimmy: My Life with James Dean A Love Story chronicled their love affair from the moment when the NYC dancer met the 21-year-old Indiana farm boy who had come to New York via Hollywood.
Elizabeth Montgomery, a star of Bewitched, was also a longtime close friend.
Sheridan began her screen career with guest shots on famous roles in Kojak, The White Shadow, and Gimme a Break!, and Star 80, and The A-Team, Newhart, Remington Steele, Moonlighting, and Murder, before landing her recurring role as the eccentric and spy-happy Raquel on ALF.
Seinfeld, which became the most popular sitcom in the 1990s, was never a quotable pop-culture favorite in reruns. When she heard that "Crazy" Joe Devola was "after" her beloved son in the 1992 episode "The Wallet," she was completely disgraced that there was someone who didn't like Jerry.
I know this may be difficult for you to understand, Jerry said of Helen. No, its not true. Youre a wonderful, wonderful boy. Everybody likes you. Its impossible not to like you. Impossible!
Seinfeld became a popular summer show on NBC in July 1989, when stand-up comedy was hot and comics were landing television programs. From there, the "show about nothing" had an uphill climb, but the program finally entered the postseason Top 25 in the Nielsen rankings in 1992-93.
Seinfeld took over the Cheers' 9-hour slot for the 1993-1994 season, ending it with a three-time no. 3 ranking. It would run no. 1 or no. 2 for the rest of its nine-season run, ending in 1998.
Sheridan was the last surviving "parent" from Seinfeld. Estelle Harris, who played George Costanza's mother Estelle, and Jerry Stiller, who played Frank Costanza, died in 2005. Barney Martin, who played Sheridan's onscreen husband Morty Seinfeld, died.
Sheridan would continue to work in films and television throughout the 2000s, including now You Know, Closing the Deal and Play the Game, and guest shots on a TV series, including Numbers and American Dad!
Sheridan is survived by her daughter and daughter-in-law.