There are many types of Gegs with different forms, but they each share two common traits; they all have egg-shaped bodies and sport insect-like wings. Each type of Geg has its own unique features.
Mech Gegs are white eggs with purple eyes and a metal mouth guard. Pac Gegs are yellow eggs with orange eyes and a mouth. Normal Gegs are brown eggs with a huge hole in their faces that reveal their brown eyes. Spiky Gegs are huge purple eggs that are covered in spikes. They have menacing, bird-like eyes which show through holes cracked in their bodies.
Due to events that occur in Green Grounds, Big Birdee and her family harbor a grudge against the Kirbys. This changes in Stage 11 of Sandy Canyon when the youngest members of the family, the Wee Birdees, are kidnapped by the Gegs. Big Birdee is grief-stricken by this. The Kirbys break the Wee Birdees out, defeat their captors, and return them to their mother. This ends the Birdee family's dispute with the heroes.
In this stage, if enough Kirbys are KO'd that a Wee Birdee is left unattended, the player receives an immediate Game Over.
The Gegs appear primarily in Sandy Canyon, though some reappear in Stage 10 of Dedede Resort. Gegs act differently depending on their type.
Mech Geg is the most common of the Gegs. It hovers over the Kirbys and attempts to crush them with its metal helmet, which instantly KOs them if successful. Mech Geg first appears in Stage 6.
Pac Geg is the second most common of the group. It does not attack, but rather summons Beanbons to attack the Kirbys. It first appears in Stage 8.
Geg is the weakest of the group. It does not attack the Kirbys. Instead, it expands its body and bursts into dust, which covers up the screen for a while. This Geg often assists other Gegs, so it is harder for the player to identify what is being attacked. Geg first appears in Stage 8.
Spiky Geg is the rarest, toughest, and most dangerous of the group. It can smash Metal Blocks without so much as a thought, pursuing the Kirbys with a vengeance. One touch from a Spiky Geg can immediately KO a Kirby. The player must use these Gegs to break down walls he/she cannot in order to obtain certain medals. Spiky Geg appears exclusively in Stage 11.
Geg's name is an anagram of the word egg, which is what these creatures are based on.
One of the giant Spiky Gegs will chase you with a vengeance. Don't let him catch up with you. But don't miss out on the medal that you'll pass as you run.”