I think fans are reacting to something that humans naturally react to, which is good chemistry between characters that you wouldn’t expect to be seen together. Stiles and Derek couldn’t be more opposite as people or as personalities. On the one hand, you have the most eccentric, animated, irritating and spaztic character in the show. And then on the other hand, you have the very serious, very “has everything on the line” kind of dark character. When you put those two together, that’s just comedy 101, so it just creates a funny and fun dynamic.
Dylan O’Brien on Sterek popularity (Da Man magazine [x])