Possible Clues:

• Dr. Seuss title animal
• Dr. Seuss's turtle
• Reptile of kiddie lit
• Dr. Seuss character who becomes 'King of the Mud'
• Seuss pond-ruling reptile
• Kid-lit title character who says 'I am the ruler of all that I see!'
• Dr. Seuss title character with a shell
• Blue-backed Dr. Seuss character
• Seussian “king” undone by a burp
• King of a Seuss pond