Tip: Make sure that ALL exit-enabled pipes, doors, etc. have a screen exit defined, or they'll take you to Level 0, the "endless" bonus game. Unless Start+Select is enabled, the only way out of it is to reset the game.
This is an egg that acts like an egg from Adventure Island (or Wonder Boy port for the NES, if you will). When you touch it, it launches upward with x-speed depending on player's. And when it lands back, it spawns a sprite.