Taro the Space Alien (Japanese: うちゅう人田中太郎 Hepburn: Uchūjin Tanaka Tarō) is a comedic anime and manga series created by Yasunari Nagatoshi. It originally ran from 2000 - 2001 in Japan. It is known to have at least 4 dubs outside of Japan: German, Castellano (Spain Spanish), Mandarin (Taiwan) and Cantonese (Hong Kong). It is suggested that the series was licensed in the Philippines, Korea and North America as well, the latter being the most mysterious considering the use of the English title in most of the international adaptations.
The plot, in summary, centers around a small-town 5th grader named Takashi Horimachi who befriends the new exchange student, Taro Tanaka. Takashi quickly realizes that Taro is an alien, and becomes fascinated by him from then onward. The pair embark on many misadventures while bumping into a wide array of friends and foes alike.
Missing English Dub
The first mention of the series in North America traces back to a press release from September 8, 2004 listing it under the handling of ShoPro. A link, tracing as far back as late 2005, shows the series under Viz Media including a localized logo. During that time, Viz and ShoPro collaborated on a number of series including Inuyasha, Case Closed and Zatch Bell.
This link from Shogakukan Production's website (the parent company of ShoPro) shows that ShoPro handled the main international distribution of the series.
While the other properties listed in the press release under ShoPro and Viz have been localized released in one way, shape or form since 2004, Taro never saw the light of day in North America.
Spain: "Taro el Extraterrestre" (lit. Taro the Space Alien)
Released sometime after 2005, this dub seems to have been a direct translation of whichever episodes or scripts that were dubbed by Viz/ShoPro. The closing sequence features only the Japanese credits simply translated into English, but not Spanish, interestingly. Shogakukan (the owners of ShoPro) and the Spanish dubbing company LUK International are featured at the beginning and end, respectively.
The opening sequence includes the Viz localized logo and is a Spanish translation of the original Japanese opening, suggesting that at least an English translation of the song exists.
LUK also produced a dub in Catalan under the title Taro, l'alienígena.
Taiwanese Dub: "外星人田中太郎" (lit.)
As seen in this particular episode, this dub seems to have been in direct relation to the Spanish and English dubs as it features the English "Viz" logo.
Cantonese Dub: "我的ET同學" (lit.)
Germany: "Taro Alien"
All 24 episodes of the show aired on RTL II in the summer of 2002 (May 7, 2002 - June 10, 2002)
The opening sequence as well as some episodes are available online, but it seems like this dub is unrelated to the English, Spanish and Taiwanese adaptations but was at least overseen by ShoPro as the above link states.