Giant Penguins were once very real indeed. In the late Eocene period, about 35 million years ago, the man-sized penguin known as Anthropornis nordenskjoeldi lived on the coasts of New Zealand.
In the modern age there have been numerous sightings of gigantic penguins in the United States, off the coast of Florida. Even larger than their prehistoric brethren, the beasts were reported to be as large as 15 feet tall, and have been spotted by groups of people on Clearwater Beach, Florida, and in the open ocean on the Gulf of Mexico. They have also been sighted by a private airplane flying over the Suwanee River. Cryptozoology enthusiast Ivan T. Sanderson has been one of those who researched on the creature, and believed it to be real, but the case remains obviously unconfirmed.
Giant albino eyeless penguins notably appear in H. P. Lovecraft's story At the Mountains of Madness, dwelling underground in the old abandoned cities of the Old Ones and serving as main food source of the local abomination known as the shoggoth.