I don't know, they're way too realistic, to the point of being creepy. I mean, they're brilliant, they just freak me out.
There's also a sense of being weird for the sake of being weird, without being natural or feasible. An enormous coiled shell hanging from the back of the head would be impractically heavy, and what use are claws coming out of the back of the head?
Well, at least people can no longer complain
Star Trek aliens only have bits of junk stuck to their foreheads.