Foreigner Excuse

Are you harboring a/an alien, angel, anthropomorphic animal, brainwashed test subject, clone, demon, goddess/god, inter-dimensional traveler, living weapon, mermaid, superbeing or synthetic human bishojo/bishonen?

Do you need to Hand Wave their bizarre behavior?

Do you live in Japan or in an area of predominantly Japanese culture? Alternatively, in case you are a non-japonese with a new artificial/supernatural/otherworldly new pal you need to hide, do you live in an area of homogeneous quaintness where Nothing Exciting Ever Happens?

Then do we have the excuse for you!

Yes, an unfortunate bit of Truth in Television is that an average Japanese person really isn't particularly world savvy, possibly even less than the stereotype of the average American. The Japanese seem to be able to blame just about anything on the influence of other countries on tourists and students. Everything from being totally unfamiliar with human social interaction, all the way to magical powers, can be hand waved under the pretext of having been or coming from out of the country. Just claim that your new artificial/supernatural/otherworldly new friend is a foreginer or spent too much time abroad and suddenly your relatives and neighbors will accept anything that come from them, from violating every unwritten rule of social interaction to suddenly gaining wings with "ah, that's foreigners for you".

The American version of this tends to require the alien/mermaid/robot/whatever to actually be from another country, most notably Estoooooooooooonia or any remote Ruritania-like territory.

If the story takes place in a rural area and the weirdness is more mundane, they can get away with the relatively closer (in geographic terms) "they come from the Big City".

Could be related to the fact that Japan's population is over 98% Japanese.

Subtrope of Wild Card Excuse, which is itself a subtrope of Blatant Lies.

Anime and Manga

 * Magical Girl Lyrical Nanoha A's: In order to explain why she had absolutely zero knowledge of life on Earth, Fate was introduced to her new classmates as being from overseas.

Film
""We are from... France.""
 * Encino Man: As mentioned above, the eponymous character's oddities are explained away by claiming he's a foreign exchange student from Estonia.
 * The Coneheads film, inspired by the classic Saturday Night Live sketches cited below.

Live-Action TV

 * Saturday Night Live, The Coneheads: "We are from... France."

Visual Novels
"Suzuku: Ah, that explains it. Nishimoto: That's someone who lived abroad for you."
 * In Princess Waltz, Liliana uses "I lived abroad" to explain how she was able to jump out of a second-story window with a friend on her back without injury.