As the link shows, if you would put it on a t-shirt, you can absolutely expect to hear from Nintendo's lawyers, so the question will just be whether you have the time to put up a fight.
And Nintendo cannot sue you if you are making the t-shirt for your own personal use.
If you make a rip-off of Star Wars, OK. Now show it to others.
Same with a t-shirt.
Of course, a lawsuit has to do with damages... what is the damage of a t-shirt 6 people saw?
But if you wear it on a TED talk?