Also I don't really see how "Derpy" as a name is that offensive, I thought it just meant to have a, well the expression that comes up if you google image derp, not a crack towards people with mental disabilities (but please correct me if I'm wrong).

Well, since you asked, I am going to correct you. This is the first image that comes up when I do a Google Image search for "derp." This one is in the top ten. So is this one. This is clearly a term that mocks the appearance and behavior of people with disabilities. The reason that the term is applied to people without disabilities making funny faces or acting stupid is because calling somebody "derpy" means "you're looking and acting like you have a disability, lol!" It's the same as calling a person "retarded." Even if you weren't aware of the fact that the term originated as slang to mock people with disabilities, the fact that there are people all over the internet speaking out about how the term is used to mock people with disabilities - even in the comments of this very post, right here - means that that's probably something you should be listening to.

I also don't see why they had they had to uncross her eyes.

They didn't. Her eyes are still crossed.