I was playing Black 2 today and decided to start catching N's Pokémon. Odd natures aside, they at least seemed to match the things he had in Black and White....until Joltik. Strangely, N's Joltik seemed to have Unnerve as its ability (no matter how many times I reset to see if it was a randomly set ability like with normal wild things, it didn't change). However it had CompoundEyes as an ability in B/W. Did it find an Ability Capsule or something while wandering around Chargestone Cave, or did Game Freak just screw up on this (especially with CompoundEyes being the better ability)?