Practically anything can go faster than Disc light, which is lazy and tame, unlike ordinary light. The only thing known to go faster than ordinary light is monarchy, according to the philosopher Ly Tin Wheedle. He reasoned like this: you can't have more than one king, and tradition demands that there is no gap between kings, so when a king dies the sucession must therefore pass to the heir instantaneously. Presumably, he said, there must be some elementary particles - kingons, or possibly queons - that do this job, but of course sucession sometimes fails if, mid-flight, they strike an anti-particle, or republicon. His ambitious plans to use this discovery to send messages, involving the careful torturing of a king in order to modulate the signal, were never fully expounded because, at that point, the bar closed.
Terry Pratchett, Mort (1987)