I'd put one in the back window of my Mustang, so when I speed off, people will see I'm a cool nerd (like Millhouse)!
I'd put one on my water bottle, so when I'm at the gym, people will think I'm a super human robot co-existing peacefully with the human world.
Or, I may just put them on my desk at work and yell out every 30 minutes, "Ooooooh! Pretty colors!"