Fluffy is what the cub at the end of The Lion King is called.The name was jokingly given to the cub by the film makers during the production of The Lion King. It was never meant to be the cub's final name.

Fluffy looks almost exactly like Simba did as an infant cub: yellow eyes, golden-brown fur, tan underbelly and a pink nose. The Major difference is that Fluffy has dark ear rings and Simba did not as an infant.

Girl or Boy?
Because the gender of the cub is never officially cited by it's creators, the question often arises whether the film makers intended Fluffy to be a boy or a girl - but the chances are they did not bother to decide it's gender because they indeed didn't announce any such decision on the commentary track and even gave it a unisex nickname. This chance is supported also by how they reveal in making-of documentaries that they didn't believe in the film's success, which supports the chance that no sequel was intended and thus they didn't bother to decide a gender for the cub.

Some theories are passed around, though. On theory is that because Fluffy has dark ear rims, (and some other girls in the films to, ex. Nala), and Simba doesn't, it makes it a little more apparent that the cub might be a girl. But this could of also been a continuity error, and is never really
mentioned by the films creators.

Who is Fluffy, really?
After the released of The Lion King in 1994, the cub became very popular object of speculation as for who it is. The film's content itself doesn't say anything about the cub apart from it's outside appearance. No name or gender is given.

In 1994, a few months after the film was released, a book series was published titled The Lion King: Six New Adventures. It became one of the most popular Lion King book series. but it was quite known, because it was only released in America. In it, Simba and Nala have a son named Kopa. Those books were not written by any of the film's creators.

In 1995, the film's creators released a commentary track for the Laserdisc released of the film, wherein they called the cub "Fluffy" and didn't refer to it as either a "he" or "she". They didn't mention Kopa in any way.

Soon enough Disney's film makers started to create an official sequel film, but the crew was all different from those who created the canon film. A rumor has it that the sequel's creators were planning to write the story with two cubs, a boy and a girl, but cut the boy out in early production and developed the story only with the girl who was later named Kiara. However no official source for such production development has yet been proven.

Why they remade the cub's ceremony scene for the actual film is unknown. Why they redesigned the cub for the actual film is also unknown. Whatever the motive, the act is retroactive continuity and is very common in fictional film series.

The most obvious and official identity of Fluffy is Kiara. Still, because of the differences in the ceremonies and the cubs and whatever other reasons in the film itself, some fans believe that Fluffy is actually another one of Simba's cubs, Kopa.

The cub is known to be Fluffy/Kiara.
Kiara as a young cub