The Blow Up Doll is an item obtained in Shay's route in Broken Age.  It is added into Shay's inventory when he opens the vent in his bedroom with the screwdriver.


When deflated, the doll resembles an inflatable raft, but when blown up, it looks like a crude model of Shay.


The doll is used as a decoy to trick Mom into believing that Shay is still asleep, allowing him to slip into the Bossa Nostra's ventalation.  After the ship makes two rescues, Shay returns to his room and pops the raft, making it fly around his room and disappear.