Giraffes can grow up to 14-19 feet tall, with their legs being up to 6 feet and their necks even longer. An alien trying to adapt to Earth would need things like hands and claws to move and grab prey, defenses against predators and the elements, and teeth to eat. If a crocodile evolved hands and feet, it would likely starve because it could no longer catch prey or swim efficiently. While humans can jump higher on planets with lower gravity, creating a single perfect habitat for 10 very different animals from cheetahs to fish would be impossible, but they may be able to adapt to a environment with varied landscapes and resources.