About T-Shirt Design
Keep Calm and Irish On T-Shirt works because it sounds more like something a real person would say than a random slogan. Fans of St. Patrick's Day will probably get the joke first, but it is simple enough for almost anyone to understand.
This would be easy to give as a gift for parties, St. Patrick's Day, or any random day when you want to make someone laugh. People who buy t shirts for the joke as much as the shirt itself will probably get what this design is going for. If novelty t shirts are your thing, this one has a simple joke that is easy to wear. Sometimes a simple joke works best, and this shirt keeps it right there.