I had a wierd run-in today. Today I was wearing my Undertale shirt, and I was out to a shop where me and my friend were hanging out, and we went to go get some McDonalds since it was across the street. After giving my order and walking to a table from filling my drink, some kid is pointing at me with this excited face and his parents turned around in this equally jubilant mood. I walked passed them and waved and said hi, and the kid got like really shy for a second or something. I walked right by to my friend and just totally loving felt wierd and was totally too high for stranger interaction. Kid either misrecognized me or something or really liked my shirt. I will never know.
He probably liked your shirt. If kids are a young age, then if they see a shirt of some sort of animated character, like a cartoon character, they will really like it, and guess will say that it's cool.
I actually remember back in the summer, me and a few of my friends were just hanging out, talking to each other. We were at a camp so bear with me. Anyway, one of my friends was wearing this foxy shirt that looks like it came from fan art. We are chatting when this young kid in a younger group goes up to us, and I am not stuffting you, he literally pointed out the shirt my friend was wearing, simply because it looked friendly. Then again, it was probably just FNaF, but still.