Smiley Bomb (スマイリー・ボム) is the fourth and final boss in Sonic Labyrinth, awaiting Sonic at the bottom of a long, Ring-filled slope in Act 4 of Labyrinth of the Castle.
Dodge the shower of tiny Eggman bombs that rain down from above at the start, and then the Smiley Bomb appears. The Smiley hovers around overhead and attacks by flying over Sonic's position and dropping a bomb. Immediately following the explosive drop, the Smiley lowers down to attack head-on at the point of impact: this is the only opportunity to attack. After 10 hits, the bottom half of the bomb disappears leaving only the creepy grinning head floating around in the air. The head attacks in the same general pattern, except rather than dropping a bomb, it vomits up a laser blast that splits into two smaller charges upon hitting the ground. Land 10 more hits on the head (total of 20) to pop the Smiley Bomb.
The boss relinquishes a Chaos Emerald upon being destroyed, and Sonic picks up another in the ensuing end sequence, dropped by Dr. Eggman as he runs away. Congratulation! A winner is you!