Creepy role: Anthony Fremont in the "Twilight Zone" episode "It's a Good Life"
You know this kid even if you've never seen this particular "Twilight Zone" episode. He has eerie powers. He can hear what you're thinking. And if he's displeased with you, then poof! Off to "the cornfield" you go, never to return. It got remade for the "Twilight Zone" movie and spoofed by "The Simpsons," but Mumy's role as the tiny terror bossing around poor Cloris Leachman is legendary. Mumy -- now "Bill" instead of "Billy" -- went on to star in "Lost in Space." He still acts today, but the busy actor in the family is now his daughter, Liliana, who actually played the equally superpowered daughter to Mumy's "Twilight Zone" character in a sequel episode in 2003. And yes, Cloris Leachman came back too.