Fifteen Strange Seconds

At 23:25 Matthew Gray Gubler walks on camera, says his line, then tries to stifle a laugh. He looks at Rachel Nichols, who does the same. In the United Kingdom, this is called corpsing, which is a theatrical slang term used to describe when an actor breaks character during a scene by laughing or by causing another cast member to laugh. [x]

(Source: pagetvbrewster)