Some of the wildest creations can be found with mydarling20: ghosts, wings, dragon backpacks, wooden toy swords, crowns, halos, gothic chokers,and most of all, the most creative Witch hats you may never use but will probably download anyway. I did.
Necrodog is making a monster factory. Just right for mad scientist Sims. There is a Monster Factory version 2 if you want to try an older version rather than risk the new test version. I also found a wizard if you want to go a bit less science fiction.