Character actress Wendie Jo Sperber enjoyed a long, lucrative career in Hollywood--though not a star, she was a familiar very face. Her specialty was exuberance and hysteria, typified by her flying leap from the moving car in "I Wanna Hold Your Hand" (1978)--the better for her star-struck 1960s teenager to try to snag tickets to see the Beatles on Ed Sullivan. It also was the first feature film for director Robert Zemeckis, who later cast Sperber in his 1980 comedy "Used Cars" and his 1985 blockbuster "Back to the Future" (Sperber also appeared in 1989's Back to the Future, Part III). Steven