Of mammals and eggs

After school conversation with my five-year-old. 

"Amma, do you know there are two kinds of animals. Mammals and not-the-mammals like birds,"
Wow, are you learning all that Nidhi, I ask, a tad bit happy that she's actually paying attention in class.
Eager to contribute my own bit of wisdom, I say, "You know birds lay eggs, and that's why they are not a mammal." 

As soon as I said that, I knew I should have shut up. "But ammmaaaaa..." Silence. The little 5-yr-old brain is whirring in slow motion and then suddenly lights up.
"You know who else is not a mammal?"

I raise an eyebrow.

"Appa!! He also gets eggs. From Tesco. So he is not a mammal, but he is not a bird either" Her expression is quizzical now.
"So," I prod on.

"So he's a Appa!"

Well, somewhere it all ties up.