Why was Muffet II portrayed by a chimpanzee?

✦Indie✦ on Instagram: "Did you know that Muffet, a fan-favorite Undertale character isn’t actually a character owned/created by Toby Fox? In Undertale’s kickstarter, Toby had a tier where if you donated a certain amount of money, you could put your own character into Undertale as a boss fight. Muffet, So Sorry, and Glyde are all examples of this. Unfortunately, because of this, we will likely never physically see them in any of Toby Fox’s games again. They are, however, sometimes alluded to in s