Dr. Seuss is a beloved children's author who wrote many classic stories. One of his most famous characters is Horton, a kind-hearted elephant who famously said 'I meant what I said and I said what I meant, an elephant's faithful one hundred percent.' Another popular character is Yertle the Turtle, a greedy king who learns a lesson about humility. Lastly, the CAT in the Hat is a mischievous feline who causes chaos and teaches children lessons about responsibility.