Former Prime Minister Yukio Hatoyama, who announced Wednesday he is retiring from politics, is leaving behind a series of quotes that at times hindered bilateral ties with the U.S. and other remarks that were borderline wacky.

Due to his appearance and possibly his unreadable character, Hatoyama was nicknamed "the alien" and enjoyed it, even before he became prime minister in September 2009.

"All humans are aliens. We are earthlings, and at the same time we are aliens, one existing part in the universe," Hatoyama wrote in his 2000 book "Seicho no Genkai ni Manabu" ("Learning from the Limits of Growth").