Minecraft wiki entry for Dragon_Egg, associated text: The writer of the Minecraft comic WonderCraft, Samcube, was requested by Mojang to create official Minecraft posters. In a part of these works, one can see an area with an ender dragon and a chicken on top of a huge mushroom. In the same scene, the dragon egg is visible near the chicken.
If the dragon egg teleports and falls into the portal, it spawns in the Overworld at the world spawn.