About T-Shirt Design
Shamrock Inspector T-Shirt has the kind of joke people can understand in about two seconds. Fans of St. Patrick's Day will probably get the joke first, but it is simple enough for almost anyone to understand.
It makes sense for parties or St. Patrick's Day, especially if the person already likes this kind of humor. People who buy t shirts for the joke as much as the shirt itself will probably get what this design is going for.
The graphic tee style keeps the whole thing casual and easy to understand. The whole point is to get a laugh, and the shirt does that without making things complicated.