Don't think you offended anyone with this but you never know

I disagree on your statement however, even with fictional characters there has to be some sort of believeability and I KNOW for a fact that even the best artist in the world if any such entity exists will not draw from memory autistic savants excluded of course.

thing is he is making an alien head of some sort on an arachnid body to make this believeable he has to get the head to "match"with the body and the arachnid body has to have some arachnid resemblance in it.
To make an exaggeration for clarifiyng purpose only ;
you can't put a clownshead on a horses body it will brake it's believeability.
You can match different creatures ofcourse but they have to have bits and pieces of each other either in color texture and/or shape to make them believeable.
So to make the clownshead believeable you could give it a horsemouth and horseears, on the body I would add clownsshoes for feet or a blow up sadle or maybe even pants with nice purple bubbles
I always collect ref images as much as i can find.