What hatches from a Retired Egg in Adopt Me?

Could you elaborate on the mysterious process of what emerges from a Retired Egg in the game Adopt Me? Have players discovered any specific creatures or surprises that are exclusive to these particular eggs? Are there any clues or hints within the game that suggest what might hatch, or is it purely a matter of chance and excitement for players to find out for themselves? And how does the Retired Egg concept fit into the overall gameplay and world-building of Adopt Me?