A nundu is a gigantic beast that can tear you to pieces with its claws, but it doesn't have to, because its very breath can kill you. Fortunately there are none of them in Britain, where I'm from. I've never seen a live one.
Betelgeuse is awfully good at delivering letters. He's useful, unlike a cat. Some of my friends think he's grumpy, but that's only because he doesn't like being bothered when he has a letter! He's actually good-tempered for an owl, just rather loud.