Whats the best nature for an intelligent noctowl?

Question

i'm catching a shiny noctowl and I want it to be similar to ash's noctowl....so whats the best nature?

Answer 1

Natures only affect the stats, the trait they get don't have any real effect, meaning it is ill advised to train one solely based on what the stat "do" rather than basing it of the stat increase it needs the most. Competitively speaking, Calm(+Sdef, -Atk) is your best bet, making it slightly less awful (but really, Noctowl is a rather bad Pokemon no matter what you do).

Answer 2

Personality-wise, I'd go with Impish. The description on Bulbapedia page seems to fit well:
>Personality-wise, Noctowl was presented as intelligent, mischievous, and cunning — although these traits weren't usually emphasized or touched upon after its debut episode.

If you wanna be competitive though, take Flaf's advice. :3

Hope I helped. :)