- For the Badniks with the same name, see Egg Saucer (Sonic Blast).
The Egg Saucer appears to be a giant wheel with a grey tire and is decorated with alternating of yellow and brown-colored strips around its circumference. It has three contraptions mounted on it which can revolve around about the wheel's center: a cockpit, a laser cannon and a giant hand. The cockpit and the laser is blue and orange, and the hand is mostly gray with some blue and orange dots on it. Each of these contraptions are mounted on a metallic stand on the wheel, which is mostly grey with a blue spherical glass on either end, a smaller blue spherical unit on the center, and orange borders with spikes underneath.
The machine will stay to the right of the stage and has three platforms: the cockpit (for Dr. Eggman or Knuckles the Echidna when playing as Sonic), a laser, and a huge hand. The laser is optional and takes three hits to destroy, it will also fire a laser with deadly aim. Next is the hand which is a great threat. Sometimes it will swing down, trying to chop the character, or it will do an open-hand slap, which results in an instant death. After the slap, the hand will stay open for a while. Touching it in this state will also result in an instant death. The cockpit has no real defense except for the laser and hand, but it can be hard to hit since it has to be hit at the very top. If hit from the bottom, the character will sustain damage.
When reaching this boss as Sonic the Hedgehog for the first time in the game, Egg Saucer is piloted by Knuckles the Echidna. During the encounter, it has its own boss BGM, but it later turns out the normal pinch mode music. After destroying the machine, Knuckles, angered, runs after Sonic with oil all over him. It was then revealed that Eggman tricked Knuckles again, and Sonic runs off to continue his adventure. Knuckles then swears revenge on Eggman for tricking him. Knuckles is then unlocked. If Sonic goes back through the stage, the boss will be Eggman instead of Knuckles.
Egg Saucer later reappears in the XX stage, the boss rush of the game. It has all attacks from the previous time, as each of parts take only one hit, and the cockpit can be damaged by doing only three hits to destroy the machine.
- According to the Prima Strategy Guide for Sonic Advance 2, the Egg Saucer was the most expensive weapon in Eggman's R&D expenses, which also resulted in the next two Eggman machines being flops.
- Egg Saucer is pointed out by fans to be the hardest boss in the game, due to the invisible laser attack from the cannon, and one attack by the hand part of the vehicle, which can cause instant death even if the player has rings.