About T-Shirt Design
If you like shirts that actually have some personality, Funpa Like Grandpa Only Cooler T-Shirt is a good example. It fits really well with grandpa humor, but you do not have to be obsessed with that stuff to enjoy the joke.
You could wear it for Father's Day, bring it out for birthday, or just keep it in the normal shirt rotation. As a novelty t shirt, it has a simple idea that is easy to notice without feeling overdone. This one is mostly about having a little fun with what you wear, which is kind of the point.