Lurker egg

The Zerg Lurker egg is a specialized mutation stage where a Zerg Hydralisk cocoons itself. While in the egg, the Hydralisk slowly transform into its Lurker form. The egg has the same HPs as a regular egg (200).

StarCraft II
In StarCraft II, the Lurker Egg reappears as the transition unit between Hydralisks and Lurkers. It is larger than a normal Zerg Egg.