Even though the entity was supposed to be portrayed as an "everyday person" it was always a little off. The actors who were cast to play the entity had to undergo makeup to make them look just a little scarier!
The Fly - Jeff Goldblum
In one of his grosses films yet, Jeff Goldblum became a human fly. The makeup in this film is utterly disgusting, which actually fits the bill. Since this was released in 1986, a lot of the gross FX was practical and done by hand.