You reach for a large, oversized football jersey, like the kind team fans normally wear. It is blue, ans has the numbers '00' on the back.
It seems like it would be comfortable to wear, what with the soft material and excess size and all. So you slip it on.
It slides on easily, and the collar barely catches on your shoulders. You're still marvelling at the size of such a jersey when your body begins to feel strange.
You're confused, because you can't quite seem to recognize the feeling. You bring your hand to your chin to try and think better when your sleeve suddelny grows tighter than it was. You look at your arm and see that it has practically exploded with muscle, bulging and rippling. And it's still growing.
You stare, then look at your other arm to see that it's growing, too. Then you look down. Your pecs are thickening and pulling the jersey as well, along with your back, you suspect. You also note that you're growing taller, but that's eclipsed by your new, growing form.
You hear a loud ripping noise and notice that the shirt you were wearing underneath the jersey has finally ripped to shreds.
Soon, the growth slows to a stop, your torso and arms stretching the jersey to the limit. You look like a fully-trained quarterback, only instead of pads, you have giant muscles to protect you.
You look down at your lower half, expectantly, only to be disappointed. They barely grew at all.
Of course, they gained a bit of strength to support the weight of your giant upper half, but not near enough to match your gargantuan arms.
"Oh, I get it!" you say out loud. "The clothing only affects the part of the body it's meant to go on."
You nod to yourself in understanding, then begin to question your sanity, as you are talking to yourself, and you do seem to be oddly accepting of impossible Genie's and magic textiles. But then you think, who cares if I'm crazy? I'm havin' fun!
So, as an experiment, you try to pull the jersey off. That is very difficult, as you've grown quite large and cumbersome, not built for delicate t-shirt removal, but for running into others.
But, soon enough, you peel the jersey off without damaging it. You then begin to shrink back to your regular size, sans a shirt.
"This is really cool," you say out loud, again.
"I wonder what else I could do...?"