Morton the Elephant Bird is the son of Horton the Elephant. He first appeared in Horton Hatches The Egg. He also appeared in The Wubbulous World of Dr. Seuss and Seussical the Musical. He appears in the first and second seasons of The Wubbulous World of Dr. Seuss.
Seussical The Musical
At the end of Seussical the Musical, Morton the Elephant Bird comes out of his egg. Gertrude McFuzz then offers to take care of Morton since Horton states, "He only knows Earth.". Morton's name is not revealed in the musical.