I hatched my Scarecrow with another wizard's Phoenix.
According to the wiki, I should have a Shadow Phoenix, but instead I got a Giraffe. In addition, according to the wiki, Giraffe is a first-generation pet. As the wiki said, my Giraffe got Spritely as his Teen ability.
How did this happen? When you hatch pets, is there some kind of percentage chance to get a random first-generation pet?