20 Biggest WTF Moments In Pokémon History

12. The Mysterious Disease Known As 'Pokérus'

Along with the various status conditions that can affect Pokémon as a result of battle, there's actually a much more unusual affliction that can strike when a new beast is obtained. Pokérus is a virus that a newly caught or bred Pokémon could be carrying, that can also be spread to your existing monsters if they're in the party together.

Despite being known as a virus, however, Pokérus isn't actually a bad thing. Pokémon that battle while afflicted will gain double EVs from each encounter, meaning that Effort Value trainers are able to benefit massively from having their team members infected.

Pokérus is actually a rarer occurrence than meeting a shiny Pokémon, by a ratio of about three to one. As of the latest generations it's a little easier to come by, though, as the worldwide trading makes the virus more accessible. Pokémon traded across games are said to have a higher chance of arriving with Pokérus, so your brand new trades may be even more useful than you think!