Of the Japanese anime that were imported to the US in the mid-60's, Prince Planet might not be on the tips of people's tongues today, largely because the series lasted just one calendar year. 52 weeks, that's all.
The series launched in Japan in June 1965, and aired without repeats for one solid year, with the finale airing at the end of May 1966. Four months later, the series was imported to the US by American International Pictures, and would appear in syndication in some cities into the mid-70's before fading away for good. Part of the reason for the series' ultimate failure was the heavy amount of violence, and the fact that Prince Planet actually killed his enemies, something that fans of the current CW series, Arrow, may appreciate.
I never saw the show, but I was able to pull up the first episode via Hulu. Enjoy.