English on T-Shirts in Japan

I'm teaching English in the evenings and today one of my students, a cute woman around 30 wore what she thought was a "fashionable" T-Shirt.
She told me she bought it used just this weekend.
(I'm always doing small talk at the beginning of my lessons.)

The text on it was "I ♡ BIG COCK".

I asked her if she knew what it means, but she said no.
I told her to look it up when she got home, because it's not appropriate for an English lesson. She laughed and thought I was pulling her leg.

But I kept grinning, so she asked me several times to explain it. Well, and I hesitatingly did.

Man, did she get red in the face. :P It was awesome.
I bet she threw that shirt out as soon as she got home.

Everybody, do your research when buying clothes with text on them!