I used these shirts as props when teaching Precalculus this week, and they worked like a charm.
After deriving the three Pythagorean identities from trigonometry, I told my class that I got these hand-made his-and-hers T-shirts for my wife’s birthday a couple of years ago. If you can’t see from the picture, one says 
After holding up the shirts, I then asked the class what mathematical message was being communicated.
After a few seconds, someone ventured a guess: “We add up to 1?”
I answered, “That’s right. Together, we’re one.”
Whereupon the class spontaneously reacted with a loud “Awwwwwwwwww.”
I was exceedingly happy.
Mean Green Math 