KWAAQ

The word KWAAQ is a misspelling of the word "quack".

Origins of the joke
It shouldn't be stressed any further that Matt and Banshee use ducks as the basis of many jokes, so this particular word (coined by Matt) stemmed from a multitude of duck jokes in one particular conversation, and it soon became a running joke within their circles, and even ended up being a 1-second long shitpost which featured a duck quacking with a screenshot of Banshee using the word superimposed over it, uploaded without context on the channel.

According to Matt, the pronunciation of the word is not simply "Quack" but the two "a"s imply that the word be spoken more slowly with an emphasis on both "a"s - namely, "Quaaaaaaaack." [literally pronounced "Kwo-ahk", 'o' as in 'clock', and a as in 'act', 'bat', and 'cat'].

Use in mainstream videos
If Matt (or someone else) points out an instance of stupid logic, or for that matter, a statement that hasn't aged well, the sound of a duck quack will play, usually dubbed over an image of Modern Sonic with the generic derpy expression (cross-eyed, with a squiggly mouth). Sometimes it is dubbed in during a moment of awkward silence, just to break it, or as a means of transitioning between the various segments of a review in place of the usual skit. It is also shown that Reggie can speak duck - the first instance being in the Sonic Labyrinth review where, if you turn on closed-captioning, Reggie says "This game is shit, subscribe to BansheePlant."

Other uses
In Dr. Pewp, the TURDIS communicates to Pewp via modulated trumpet sounds, which Pewp explains is the language of KWAAQ. The word is also used as a Robotnikland entry coder password in Sonic: The Classic Adventures.