He helped to conceive the Nickelodeon TV show concept "Space Cases," which owed a lot to the old "Lost in Space" he co-starred in. He was the original choice for Eddie Munster on the old show "The Munsters." He didn't get the role as his parents didn't approve of the make-up he would have to wear. He eventually guest-starred as a hateful trouble-making little brat on the show named Googie. Mummy and the official choice for Eddie Munster, Butch Patrick still remain close friends. When TV Guide listed their top 100 television episodes of all time, two of them starred Bill Mumy. He starred in the original CBS "Twilight Zone" episode "It's A Good Life" where he played the all-powerful demon-child Anthony Freemont and revisited the role in the sequel "It's Still A Good Life" forty years later on the UPN 2002 revival of "The Twilight Zone" along with his original cast-member Cloris Leachman.