The Vault Boy puppet is a hand puppet based on the image of the Vault Boy, a mascot of the Vault Tec corporation. One such puppet was put in Vault 77 as part of that vault's experiment, as the vault was to house only one man and a crate of puppets.
At one point, the Vault 77 Dweller seems to hear a voice from inside the crate and discovers a Vault Boy puppet he missed. Soon, the King puppet is 'murdered' and found with his head ripped off. The Puppet Man asks the Vault Boy puppet if he did it as he doubted Granny or Reverend Hound could ever do such a thing. Vault Boy tells him that not only did he do the crime, but Puppet Man was his accomplice. Puppet Man realizes that Reverend Hound (apparently also the sheriff of his make-believe reality) will come for them both and decides to leave the Vault. His initial excursion lasts less than a minute; right after he opens the Vault door, he encounters a 747-sized Radscorpion holding a car in each claw. He immediately closes the door and decides to "sleep on it."
The Vault 77 Dweller is eventually successful in leaving the Vault, and acquires a giant ant named Mr. Pinch as a mount. He is very optimistic in regards to the outside world, noting while it was hot for December, he wasn't really a snow person. He encounters a mysterious Ghoul with only one arm, wearing a vault suit without a visible number, possibly one of the evacuees from Vault 12.
He is later seen captured by two slavers and warns them not to mess with his Vault Boy puppet as he is crazy and has "killed before". One of the two slavers contemplates whether to make him a slave or if he should serve him as food, the second remarks that he is pretty hungry. He killed the first slaver, Bob, and tracked the second one to the slaver's base where for the first time he was called by the nickname The Puppet Man.. In the end, it is not known what has happened to the man or the blood-stained puppet who both disappeared with a smile on their faces. Vault 77 was labeled as a bad idea, but the comic reminds that "the Vaults were never meant to save anyone." 
The Vault Boy Puppet appears only in the One Man, and a Crate of Puppets comic by Penny Arcade. As reference to the comic, real-life copies of this puppet were given out at Penny Arcade Expo (PAX) 2008.
- 777 real life Vault Boy puppets are available as Fallout merchandise on the Bethesda Softworks store, being shipped with the limited edition Vault 77 hoodies.