How can you tell if the reality you experience is "real" or is just a giant computer simulation? Philosophers realized long ago that of course you cannot; Hofstadter and Deutsch make the a posteriori obvious point that the question itself is meaningless. Any physical process may be viewed as a computation and therefore a "simulation".
But what if we allow the possibility of simulator malfunctions? Address errors, memory leaks, unknown-error-must-shut-down type things. What would it feel like to be in a simulation that suddenly displayed such artifacts? Parts of your universe are working fine as before, but you might locally observe very strange discontinuities and irregularities.
There are sophisticated theories of spacetime defects that I lack the mathematical apparatus to understand (any quantum gravitists want to help out?). Might any of these defects be explicable as computer bugs in the universal simulator? Could one at least get a decent sci-fi story out of this? I'm sure this vein has been already explored -- can anyone point me to a good story? Anyone up the the task of writing one?