About T-Shirt Design
You do not have to think too hard about I created a Monster, She Calls me Dad T-Shirt. The joke is right there and it gets the point across fast. The dad humor angle gives it a little extra personality without making the design too busy.
It makes sense for birthday or Christmas, especially if the person already likes this kind of humor. Fans of sarcasm shirts will probably like that the joke is direct and not too polished. For a funny t shirt, it keeps things pretty straightforward and lets the saying carry the humor. It is not trying to be deep. It is just a funny shirt with a good line on it.