Beards
I've had a beard most of my adult life, but I currently work for a large company that doesn't allow that. I'm not protesting or even trying to complain, it's just that I like growing a beard and most specifically - not shaving.
I had the idea for this shirt about a year ago when I was discussing my facial hair (or the lack thereof) at the moment and I told her that I had a beard on the inside.
I think it's pretty self-explanatory.