You are hereby honorably discharged from your duties as a Japanese citizen

Talking about the "most famous" Japanese person outside Japan turns into a generation issue I would think, but I don't think that it would too far off to say that the wife of the late John Lennon of the Beatles, Yoko Ono probably is at least one of the most well known Japanese people world-wide.

However, something I find quite amusing is the ambivalence towards Yoko Ono that the Japanese media shows to her here in Japan. It is true that Yoko Ono has spent most of her adult life outside Japan (I'm not sure if she's now a naturalized US citizen or not, but I would guess that it's not unlikely). Her Japanese is of course completely fluent during the rare occasions that she does an appearance in the Japanese media (to my surprise I once saw her in one of those stupid variety shows with comedian duo 99) but her mannerism gives her away as a long time expatriate.

The thing that I find most amusing though, is that when her name is written in Japanese, they almost always chose to write it in the Katakana alphabet and not through the Chinese Kanji Characters (the Katakana alphabet is primarily used for foreign words/names). So in the media, it's written as "オノ　ヨーコ" instead of "小野 洋子". Since the katakana alphabet is primarily used to write foreign names it gives quite an odd impression, particularly since she was born in Japan and thus have formal Chinese characters.

I'm not sure whether it's her idea to have her name written in katakana or whether it's the media that for some reason has chosen to write it like that; but it does give an impression of "non-Japaneseness". Considering that she otherwise is usually treated with some amount of respect here in Japan (although most Japanese people probably doesn't care that much unless they're Beatles fans), but it gives an impression of her having been honorably discharged from her duties as a Japanese person. Remember, don't ask, don't tell!