Grumpy Cat gets her sour look from a genetic disorder. Another type of genetic disorder has created cats with extremely short front legs that are nearly useless for holding weight. As a result, these cats, dubbed squittens, act like squirrels and mostly hop using their hind legs to get around.
Squittens are basically lovable cats that can still live a normal life. They just have to walk around differently and adapt to their unusual physical circumstances.