I laughed the first time I saw the shirt. "I'm With Stupid," with an arrow underneith pointing to the right. It was funny because the star of the football team, who everyone knew couldn't add 2+2 together without serious help, walked next to him. I doubt either one realized what was going on, and when they saw me laughing, I have no clue what they thought I was going on about. Whatever. The arrow should have been pointing at the entire high school life anyway, right?
It wasn't until a few years later that I fully understood the significance of the shirt. I was at a college party with plenty of booze and weed (and probably a bunch of other stuff that I didn't see) when I saw a guy wearing the shirt. He knew exactly how to use it; he'd purposely walk up to people and stand next to them. It gave everyone a great laugh, and when the person he was pranking caught on, they'd smack his shoulder or punch his arm and laugh, too. It was a great social lubricator - even better than the alcohol and illegal substances.
Now when I see the shirt, it's usually worn ironically by someone who wants to make a statement by not making one. You know the type, right? The world is a horrible place, and they have all the answers. Only they won't share, because they're too cool for all that. Typical.