Out of all the auburn-colored lemurs, Willie is the darkest.
In the episode, "Empty is the Head," it is revealed that there has been a feud in his family going in for 10 generations.
Willie is the only named non-main character lemur to appear in the Madagascar franchise.
Willie, although an adult, is possibly younger than a lot of the supporting characters, since he acts more perky, has a young voice, has a skinny, fit build, isn't married, and has a fast metabolism, which was shown as he was able to eat an inordinate amount of fruit and still look the same.
In Willie's binge-eating scene in the episode, "He Blinded me with Science," the artists omitted making his eyes their normal green color, leaving them a light yellow.
Willie has a more or less propensity to steal, shown when his house was surrounded by Clover and the rest of the Ringtail Guard because he stole King Julien's boom box. Willie was however beat up by King Julien, who then ran off with the boom box. He however got upset when Pancho planned on stealing something.
King Julien cried when he thought Willie drowned.
Next to Mort, Willie has the highest voice out of all the male lemurs.
Willie was never called by his implied real name, "William" until Season 4 in The Good Book.
Willie is aware of his cowardly nature, and has even admitted it.
Willie's name is sometimes mistakenly spelled "Willy."