The title of this episode is a line from "Psycho", which Kevin Williamson borrowed for "Scream".
The title of the episode, "We All Go A Little Mad Sometimes" is a quote from the horror movie Scream, also written by Kevin Williamson.
Hashtag during the airing was #ThatVampCray
"We All Go A Little Mad Sometimes" is a direct quote from both the 1960 and 1998 versions of the film Psycho. It was also a quote that was used to reference Psycho in the well-known slasher-flick Scream, which, coincidentally, was written by Kevin Williamson, the original showrunner of The Vampire Diaries. It was the Scream series that launched Williamson's career.
Damon tells Stefan to Pay the Piper - this is a reference to the fable "The Pied Piper of Hamelin ", who was hired by a village to get rid of all the rats, which he did. When the village refused to pay him, he played a different tune, and let all the children to death. A cautionary tale about paying your debts or bad consequences will follow.