The original joke was likely intentional on Toriyama's part as May 9th can be read as Go (5) Ku (9).
Ironically, in real life, Japan declared May 9th 'Goku Day'. Sites like Tumblr leapt upon this meme with repostings every, you guessed it, May 9th. ' Explanation After briefly taking over the world in the original Dragon Ball, King Piccolo declares that May 9th will be celebrated as a holiday dedicated to himself which will end with him destroying a city decided in a lottery (the dub changed the date to the 13th).
