The fascination with foreign script, especially English, printed on garments has long been strong in countries like Japan.
The actual meaning of the word or phrase used doesn't really factor in whether or not it gets stampted on a t-shirt or the front of a baseball cap. Sometimes random song lyrics, or buzzwords pulled from magazine articles, find their way onto the clothing sold by otherwise respectable retailers.
Additionally, grammar doesn't really matter most of the time, so long as the finished product looks cool.
The photo to the left is from a while ago at Jingu stadium. The grammar is fine, but it definitely qualifies as random.
In case you can't make out what it says, I'll rewrite it here, "If you start throwing hedgehogs under me, I shall throw a couple of porcupines under you."
