Fantasy Earth
Far back in prehistory, mana and magic appeared on Earth, changing the development of civilization and warping animals and plants into new species all over the planet. The bones of the planet are the same, and continents and oceans look familiar to someone from our Earth.
Someone dropped into a forested wilderness could be forgiven for thinking that they were on Earth. Forests are filled with familiar plants and animals.
...But then a completely unknown creature would appear, or a city would be in the wrong place, or a person could be seen flying through the air unassisted, and it would become clear that, no, this is not Earth as we know it.