The Scumbag Brain first appeared on Reddit in March of 2011 as a derivative of the popular Scumbag Steve meme. The Scumbag Brain represents all the frustrating thoughts and actions our minds inflict on us, pointing out that there is just as much douche-baggery within our own heads as there is in hedonistic Steve's entire persona. Even if the Brain isn't always wearing such a douchey hat.
The humor in Scumbag Brain is simple. It shows an image of a hovering brain, similar to yours or mine, and first describes a scenario which everyone has experienced at one time or another. The line that follows is the Scumbag reaction to said scenario, generally a soul-crushing, rage-inducing response that is beyond our control. Bodily functions and unwanted thoughts are the primary results, something that everyone can sympathize with and, unfortunately, seem to happen more often than any of us would like.