Dr. Reid was Prince Charming, but we already knew that.
In order to catch a female UnSub who believed her life was a fairytale, Aaron Hotchner asked Reid to approach her in a way that Prince Charming would. That way, it would reduce the likelihood of Cinderella killing herself—or her captive. Naturally, Reid played the part of Prince Charming perfectly. Swoon!
Season 10, Episode 6 "If The Shoe Fits"