The intriguing little creature depicted in the photographs is commonly misidentified as a "legged fish" or a "fish with legs and hands". Some postulate that the images are actually fakes created in an image manipulation program.
In fact, the photographs are genuine, although they do not depict a fish. This creature is an Axolotl or "Mexican Walking Fish". The Axolotl is an amphibian, more specifically, a salamander. Although they are native to Mexico, Axolotls have become popular as exotic pets around the world. In captivity, they are housed in an aquarium and can have a range of colours.
Like some other kinds of amphibians, the Axolotl generally remains permanently in its larval form. According to axolotl.org:
Ordinarily, amphibians undergo metamorphosis from egg to larva (the tadpole in frogs is a larva), and finally to adult form. The Axolotl, along with a number of other amphibians, remains in its larval form throughout its life. This means that it retains its gills and fins, and it doesn't develop the protruding eyes, eyelids and characteristics of other adult salamanders.
Although there is no mystery or manipulation involved, these photographs certainly depict a fascinating little animal.