The Egg Frog (エッグフロッグ,Eggu Furoggu?) is the seventh boss in Sonic Advance 2. It is the boss for Egg Utopia and is controlled by Dr. Eggman. The player has to hit to the cockpit eight (six in easy mode) times to destroy the Egg Frog completely.
The Egg Frog's appearance actually looks more like a spider than a frog. It is mostly gray, with yellow headlights, orange parts on its legs, and dark-gray feet. An Egg Mobile takes up most of its body.
This battle is centered on an endless hall where Rings will generally spawn in mid-air. Touching the Egg Frog's feet will damage the player. Unique to this fight, the player has the ability to invert gravity with Up (while on the ground) and Down (while on the ceiling) on which is essentially useful in avoiding the Egg Frog's attacks in this battle. Its attacks include:
The Egg Frog will leap from one surface to the other, dropping a missile on the surface it stood at, which explodes into a trail of fire when it lands. A Spin Jump alone will not be able to avoid this attack so the player will need to invert gravity as well.
The Egg Frog can slow down, causing it to move off-screen to the left. It will eventually slide back on-screen at the opposite surface with a burst of speed in attempt of a surprise attack at the player.
After four hits, Egg Frog goes into pinch mode. Once hitting the Egg Frog four more times, it will be destroyed.
Egg Frog later reappears in XX, the final Zone of the game which serves as a boss rush. There, it has the same beginning movements like in original fight and after that, it mostly does the same attack patterns. However, it only takes four hits to be destroyed.