Boss Galaga (ボス・ギャラガ) is an enemy from the game Galaga. In Galaga, it uses a tractor beam to take one of the player's ships and turn it into an enemy ship.
The Boss Galaga item, when thrown, will circle around a few times before hovering in the air. It will then swoop down on a selected enemy and use its tractor beam to "abduct" the fighter and carry them away to the upper blast line. It will also deal 1% damage to the abductee, in order to make the kill count for the player who threw it. It can be shot down, however.  If you get caught, you can escape it by Button mashing, although it gets harder to escape the more damaged the caught player is. Pac-Man uses the same animation for his Grab.
Boss Galaga appears as a Blue Trophy item that, when used, will teleport the user to a random spot on the map.
There is also a battle mode that occasionally happens called Boss Galaga Battle where players fight on random stages with the only item being Boss Galagas.
A boss enemy from Galaga. When thrown, it will spiral skyward and hand out for a time and then descend and pull in fighters with a tractor beam. If you get caught, try to escape by wiggling around as best you can. Unfortunately, there is no bonus fighter for defeating this enemy...
- Arcade - Galaga (1981)
The Boss Galaga returns in this game as a throwing item, having the same effect as in Super Smash Bros. for Nintendo 3DS and Wii U but strangely only being able to be spawned on some stages. On those stages, it can cause a Star KO if it is allowed. This can be an indicator for finding out if the stage allows a Star KO.
There is also a spirit of Boss Galaga, represented by Pac-Man.