Dylan O’Brien pulls off a very difficult physical transition between scared teenage Stiles and the Stiles that is possessed by an evil Japanese demon. It was interesting last week, but much more impressive in this episode. Evil Stiles walks differently, holds his jaw differently, makes different expressions, looks much more confident and dare I say dangerous, and it’s really an impressive bit of physical work from the young actor. Even his line delivery is different than it is as Stiles. It’s some impressive stuff, and proof again that O’Brien is the best actor on the show, and one of the best young actors on television right now.

A Review of 'Riddled' by Ron Hogan at Den of Geek. x 

Happy 22nd Birthday Dylan O’brien! (August 26th, 1991)

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])