Wrinkle - to cause or make a small ridge or furrow on a smooth surface :: Alex's notes: the verb to wrinkle suggests that something has changed or altered a smooth surface - and in a random or uneven way. Also this change is not great or very big. This is the big difference between wrinkle and crease. EXAMPLE: I wrikled the paper :: the paper was smooth, I changed or altered it so now it is not smooth, and although I did this, it is not so greatly changed that maybe the paper is useless or very damaged. We use this word with skin and getting old, but the meaning is now extended to imply something even more. We now use this word, as a noun to describe a problem which might hurt some plan or idea. EXAMPLE: I was going to drive home for Christmas, but my car is broken, so there's a wrinkle in my plan.
Crease - to put a line, mark, or ridge made by or as if by folding a pliable substance :: Alex's notes: unlike a wrinkle, the crease happens with some pattern or some design and in fact, it is usually a straight line. If you fold a paper evenly or fold it in half, and then open it back up - you can say either 1) The paper has a crease in it - or I creased the paper or 2) The paper has a fold in it. :: More notes: the difference between crese and pleat - see the definition of pleat below. A crease doesn't mean that something must be currently be floded over, just that is has this line or mark that could have come from being folded.