Alien Mothership is a boss present in Ultimate Omelette. It appears at the end of the Lost in Space... and Time! chapter, guarding a portal.
The Alien Mothership only has one attack - occasionally shooting an S-shaped projectile down, similar to the Retro Invaders that appeared in the same chapter. Once its darker parts have their health depleted, they will fall. It's possible to crash into them while they're still onscreen.
It's a huge mothership made out of pixels. Editions don't change it.
It is only encountered once at the end of the Lost in Space... and Time! chapter. It consists of 85 parts which have 2500 health each and give 2500 points after enough health is depleted. In total, it has 212500 health and gives 212500 points. Only the lowermost parts of the ship, the ones with darker pixels, are vulnerable. Once their health is depleted, they will fall down, and a Gift may spawn. If the last row of the Alien Mothership is destroyed piece-by-piece (not with a Missile), you will receive one Satellite. The Alien Mothership has no weaknesses, nor does it have any strengths.
When the fight starts, try to chip away one of the sides of it. This way, you will have a safe area when the Alien Mothership descends low enough. The chipped off parts will fall down, and you may be able to crash into them, so don't be too reckless when attacking them. The Barbequer is recommended for this fight, as its flames can remove the falling parts. Missiles also clear this boss easily, but you can't use them if you want to receive the bonus Satellite.