Gertrude McFuzz

Gertrude McFuzz is a minor Dr. Seuss character in a titular segment in Yertle the Turtle.  However, she is the deuteragonist of Seussical the Musical.  She is the loyal bird neighbor of Horton. She loves him but is shy due to having only one feather for a tail. She has major insecurities about her tail and seeks help from Mayzie La Bird because she has a tail Gertrude envies. Horton eventually falls for her and she becomes the adoptive mother of the elephant bird in the end.

Trivia

 * Being non-canon, Seussical is the only Dr. Seuss title in which Gertrude has a more primary role, serving as Horton's lover, Mayzie's neighbor, and the Elephant Bird's adoptive mother.