About T-Shirt Design
The joke on Most Likely To Pull an Irish Exit T-Shirt is easy to understand, and that is a big part of why it works. The St. Patrick's Day angle gives it a little extra personality without making the design too busy.
It works for parades and St. Patrick's Day, but it is also the kind of shirt someone could wear whenever they feel like it. It has that sarcastic t shirt attitude people like when they want something a little more blunt. As a novelty t shirt, it has a simple idea that is easy to notice without feeling overdone. It feels casual enough for normal days but still has enough personality to get noticed.