People remember real, interesting, and engaging characters. Animated characters should be pleasing to look at and have a charismatic aspect to them; this even applies to the antagonists of the story.

Appeal can be hard to quantify because everyone has a different standard. That said, you can give your character a better chance of being appealing by making them attractive to look at. This doesn’t mean they have to be “pretty.” It is about making them engaging to look at.