The Giggle Loop is a Jeffism.
According to Jeff, when something bad or depressing happens, and you want to laugh but stop yourself. Then you think about how awful and funny it would be if you actually did laugh, which makes the urge to laugh grow more. Which in turn, leads you to think about how big your laugh would be now if you laughed at this point- during a solemn/bad/depressing time/situation, which grows your urge to laugh almost exponentially - almost in a head-exploding manner. It can go longer, depending on the person tempted to laugh.