What do you call a hedgehog and an echidna?

That's a tricky one! While both hedgehogs and echidnas are spiky creatures, they are not closely related. They're actually examples of *convergent evolution*, meaning they developed similar features independently because they lived in similar environments and faced similar pressures.

So, there's no specific word to describe a hedgehog and an echidna together. You could say:

* Two spiky creatures

* A hedgehog and an echidna

* A mammal and a monotreme (echidnas are monotremes, meaning they lay eggs)

It depends on the context and what you want to emphasize!