The Split was an event that happened some point in mid-2015, when the Mikey555 Universe suffered a catastrophically high influx of fragmented information and objects from The Real World, raising instability by several thousand times the normal levels, causing the Mikey555 Universe to shatter into many, many different worlds. Whatever caused the surge that raised instability is a mystery, but it seems to have affected Mikey555's control over his universe.
As of September 28th, 2017, the Mikey555 Universe appears to be slowly putting itself back together. The ETA for its completion is unknown.