I was in my Minecraft building world and i was in the nether when I saw a thing floating in the sky. It looks like a strider's texture when it has a saddle on, but the parts were floating everywhere. It also has 3 pixels from a zombie pigman. Relogging did not help change it to normal. I am am too scared to rejoin my world to provide a screenshot, but I know some java, so I think the problem is improperly loading the texture files. That was the only ghast I saw, so I dont know if it happened for other ghasts too. all other entitys were fine. I don't know how it happened so unfortunatly i dont know how to reproduce.
Are you using any Resource Pack? If not, I have heard about glitches like MC-190067 which sound similar to this.