Fridge Brilliance is a term that describes something that seems stupid when you first see it, but upon further reflection (and possible fanwank-y explanation) makes perfect sense.

I always thought that the "Heinrich maneuver" described in Unwired was a cheap handwave that didn't really explain anything. However, in one of the stories in Renraku Arcology: Shutdown, they show one of Deus' otaku solving a binary satisfiability problem really fast. As you all know, SAT is an NP-complete problem. So either the otaku have proven that P = NP, or they just have an incredibly efficient reduction to a polynomial-time algorithm. (With good coefficients!)

What bits of the 6th world (plot-wise or mechanical) have you managed to retroactively justify?