Bye-Bye! BOXBOY! is the third and final entry in the BOXBOY series. It adds new block mechanics as well as box children for puzzles.
The biggest new mechanic are the box children. Qbby has to guide them through the level to unlock certain doors. They avoid hazards and move forward when it's safe. There are also new the Box Rocket, that fly up when used, and Box Bomb that explode in a cross shape. The Box Warp allows Qbby to teleport to the farthest box placed. The Box Remocon allows Qbby to move the boxes remotely.
There are 22 Worlds with 150 stages plus 40 challenge stages
The game supports the Qbby amiibo and the Kirby amiibo. The Qbby amiibo turns the screen into a Game Boy color palette. Each supported amiibo unlocks a costume. The Qbby amiibo's effect have been merged into the game as unlocks for playing past entries or completing the game in the Western release