[Leaftail]

Isshu is the only main-series region that does not have an O sound in its name.

Rotom joins Magnemite and Magneton as the very few Pokemon to change types the generation after they were released. All the alternate formes change their Ghost-type to that of their signature move.

Isshu currently has the fewest number of routes in any main-series region - 18. As of Heartgold and Soulsilver, Johto has 20 routes, but was tied with Isshu in Gold and Silver.

The Elite Four of Isshu all have only four Pokemon, and can be battled in any order.

Generation V has the highest number of Pokemon of any generation, with 156.

The ???-type was removed in Generation V. Curse was made a ghost-type move.

The only two Bug-types that can learn Fly are both from generation V - Urugamoth and Genosect. Neither are Flying-type.