From Monkey Island wiki
Bob is LeChuck's luckless First Officer from The Secret of Monkey Island, a ghostly skeleton who is continually losing his head, literally. He first appears to tell LeChuck about Guybrush Threepwood's arrival on Mêlée Island; he offers to take care of Guybrush, but LeChuck didn’t want it to be done by amateurs. According to this conversation, LeChuck captured the ship Bob was on, killing everybody on board, and forced Bob to serve on his ship.
Bob also reports on the successful capture of Elaine Marley, just before LeChuck bursts from his disguise as Sheriff Fester Shinetop. He later appears aboard the ghost ship below Monkey Island. Bob doesn't hold any ill will against the living, and appears courteous to Guybush and his crew after LeChuck sets sail without him. Bob seems to have a tendency for sarcasm as he unenthusiastically states how "lucky" he is to be killed by LeChuck and forced against his will to serve on his undead crew.
His last appearance is near the end when he misses the boat as LeChuck leaves for Mêlée Island in order to wed Elaine at the Mêlée Island church (he had to rescue his fallen head from the lava). Here he is confronted by Guybrush who can choose whether or not to dissolve Bob, who will gladly tell where LeChuck is going. Depending on the actions the player has taken so far, either Herman Toothrot or Guybrush's crew (Meathook, Carla and Otis) will show up to take him back.
Additionally, if the player insisted on spraying him, Guybrush will indeed spray Bob with the root beer while his back is turned before Herman or Guybrush's crew arrived. If Herman shows up he will offer Bob a ride on his ship and only agrees to take Guybrush along if he promises to save him. If Guybrush's crew appears they greet Bob as an old friend of theirs while Guybrush tells them that they must return to Mêlée Island.
Bob does not appear in any future games, implying that perhaps the scenario involving his demise was actually established as the canon scene by the development team. However, he is mentioned in passing when Guybrush first encounters Murray in The Curse of Monkey Island: he may choose to ask "Can I call you Bob?"
- Bob seems to have a fondness for music, as he is seen at one point conducting a small band of ghost pirate musicians, rhythmically bouncing his head between his knee and shoulders.
- He is voiced by Rob Paulsen in the Special Edition.