I used to live in Japan, and saw people wearing shirts with weird English pretty much every day. The really hilariously bad or inappropriate ones are vastly outnumbered by ones that are awkward, incoherent, or just plain odd. Even when the English is more or less correct it’s often not the sort of slogan you’d see on a shirt in the US.
I sometimes asked my students about their “English” shirts, and even those who spoke English very well admitted that they bought these shirts without even thinking about what they actually said. It’s just a design element. Funnily enough, I don’t think I EVER saw a Japanese person wearing a shirt that had a slogan printed on it in Japanese. Schoolkids had gym shirts with the names of their schools on them, but otherwise I never saw any Japanese writing on shirts.
From my personal collection, all purchased at mainstream Japanese department stores:
“Mellow Bing” (with a picture of a cherry)
“Addicted to Be Happy Celeb”
“Mannish Girl: Tomboy” (I love this one!)
Front: “A Phrase by My side. Forever learning. Forever young.” Back: “A Phrase by My side. Forever learning. Forever young. We never know how we really look from behind, do we? I know I shouldn’t make promises I can’t keep. Japanese Style.”
Over the chest: “The place which can feel at ease in the city.” Then there’s a picture of a cafe called “Cafe Forest” at the bottom corner, and in smaller print: “An eye is closed and it breathes deeply, slowly. If it does so, the power of the shoulder can fall out and relax. And if an eye is opened quietly, there will be very delicious coffee and a handmade cake at hand. This is a forest in a city. Please become thinking that it returned automatically and pass calmly.” (Really.)
After working as an English teacher in Japan for some time, I started to understand where some of this weird English came from. A lot of it seems to be the result of using a dictionary or computer program to translate Japanese into English. For instance, I’d bet that the “Tomboy” shirt is the result of someone looking up the definition of “Tomboy” in a bilingual dictionary, then translating this back into English literally.