He is only called Vault Boy in the adverts. He was never mentioned by name in the game. Then in Fallout 2 "pipboy" was mentioned in such a way when you updated your PiP that I thought that he was called PiPboy. So that confused me for a bit. But PiPboy and Vault Boy are two different mascots. And Falloutboy is a band.
Merry Christmas. Don't let the mutants get you.