Penguins aren't exactly formidable creatures, are they? Although Emperor penguins can reach up to 4 feet 2 inches, they always seem super friendly and cute. Now imagine a penguin the same height as you. That changes things. Penguins the size of humans... the idea sounds like it comes from science fiction. But it actually just comes from science. It was recently discovered that giant penguins used to exist. We are not kidding.