In the scene where Nancy is chased into her house by Freddy, she begins running up the stairs and her feet punch holes in the steps which are filled with some kind of a plaster-like slime. When Nancy makes the first holes, look at the next stair that she will step on and you will see that the foot holes are already there for her, but the slime is the same color as the stairs so I guess it was supposed to blend in...but it didn't