The fourth game (UO) is similar to Revenge of the Yolk. It has 120 waves across 12 levels. It includes weapons which can be upgraded through 11 power levels, with a supercharged 12th level. The weapons from Revenge of the Yolk are available as \'unlockables\'. Ultimate Omelette unlockables can be purchased individually by collecting keys, which are dropped from destroyed enemies during the course of the game. A new feature in this game is the capability of the player\'s spaceship to face in any direction depending on the level (it was always facing up in previous games), and the camera can also zoom in or out depending on the wave (boss fights typically have the camera zoomed out to contain all the action).
The plot begins with the player/hero at Space Burger. A portal suddenly opens and a ship comes out. The ship says its name is Hen Solo and urges the hero to follow him to his galaxy to see the Chickens\' latest creation, the Egg Cannon. The player heads through his galaxy and other strange places to confront the Egg Cannon.