The protagonist starts out as an egg, and as such, is simply a small white oval. When it obtains the Hatch powerup, it becomes a white bird. As a bird, the protagonist has two wings, each as big as its body, two black eyes, and two little stick legs.
The protagonist exhibits no personality traits in the game and can only be determined through silent actions. Judging by what the player must do to advance in the game, it can be surmised that the protagonist is fearless and determined, not weakening even at near-death and not afraid of the dog-headed ghosts with the purple aura, which have proven to be highly dangerous.
The protagonist can do nothing but jump in the early beginning of the game. As the game progresses and the player collects more and more powerups, the protagonist is able to do much more, the maximum of the egg's abilities being able to shoot fireballs, divebomb, bounce off of red energy, cling to the ceiling, teleport to other save points, and duck as well as jumping higher and double-jumping.
When the player collects the Hatch powerup, the protagonist becomes a bird, and as a bird, is able to get much farther in the game and therefore, collect many more powerups. The bird will be able to do much more than the egg was able to, the extent of the bird's abilites being able to shoot ice shots, crawl along the ceiling, breath underwater longer, magnetically attract crystals to it, bounce off of yellow energy, and talk to other birds, as well as everything else the egg could already do.