I've got a question about this Thundurus. It says that it's got an "Invalid PID". However, since a roamer Pokemon's PID is generated using directly the first 32 bits of the seed, every PID should be possible and legal.
Asking at the IRC, they've told me that Pokecheck maybe marks that PID as invalid because it follows a 4th gen PID-IV relationship. However, even if it's really difficult that a 5th gen Pokémon follows the relationship, it's not an impossible thing: it's possible to have any PID, even if having a method 1 PID shows that possibly the Pokémon was generated using pokesav/pokegen.
So, is that Thundurus' PID illegal just because it follows the PID-IV relationship?
In that case, wouldn't be more logical to say that, even if it can't be proved that it's illegal, it probably is because it follows a relationship that doesn't have to (but not musn't) follow?