Quote Originally Posted by Pendulous View Post
Yes, but surely we've seen couples in the background that were different types. All we can really do is trust Mr. Cake's "explanation". Though I can't imagine the science behind that. Which type of pony is recessive, and how does that work with three instead of two?
It's a world where ponies manually manipulate nature. For all we know the Cakes decided to have a unicorn and a pegasus.