Charles William "Bill" Mumy, Jr., is an American actor, musician, pitchman, instrumentalist, voice-over artist, and a figure in the science-fiction community. He is most famous for his many appearances on TV as a child actor in the 1960s.
The red-headed Mumy came to prominence in the 1960s as a child actor, when he was credited as Billy Mumy. His most notable role was in the 1960s CBS sci-fi television series Lost in Space, where he played Will Robinson, the youngest of three children of Professor John and Dr. Maureen Robinson and friend of the pompous and nefarious Dr. Zachary Smith. "Danger, Will Robinson!"—a line frequently spoken by the character of the Robot —has become an iconic phrase in sci-fi culture.
He later appeared as lonely teenager Sterling North in the 1969 Disney film Rascal with Steve Forrest. He was cast as Teft in the 1971 film Bless the Beasts and Children. In the 1990s, he had the role of Lennier in the syndicated sci-fi TV series Babylon 5, and also served as narrator of A&E Network's Emmy Award-winning series Biography. He is also notable for his musical career, as a solo artist and as half of the duo Barnes & Barnes.