The joke would work fine as Post Traumatic Dumb Shit, I think. I bet there’s other better ways to construct it too, if you don’t think that scans.
That’s if you don’t want to be buried in ableism accusations when you use it, which are, imo, getting in the way of this fine little meme.
It loses the association with “unfortunate things that happen in your head” problems, but Downs and PTSD are different categories of things anyway. Inherited vs inflicted, permanent vs temporary, etc. Doesn’t quite work.
People these days are too knowledgeable not to have that part screw with their ability to laugh at the joke, even if they understand it’s not malicious at all.
My at a glance understanding of the joke is that the… young boy character? does not understand the words he’s using. Not fully, anyway. Bit if a bone apple teeth situation.
Which is to say, I don’t think it scans. Dumb shit sounds to me like a school boy dunk and not confusion. I think different D and S medical terms could work pretty well, though.
Its funny, but we got to stop making fun of disabled people
but the joke isn’t even about Down’s Syndrome, it’s about this kid being an idiot
And that almost makes it worse. The joke works without it, why add a Down Syndrome punchline at the end? If it’s not about it, why bring it up in the first place?
because the bottom text is something an actual dumb kid said, demonstrating that he had no idea what PTSD is, or Down’s Syndrome for that matter
Everyone should be allowed to participate in humor. Whether that be as the hero or the fool of the joke. Or in this case a tertiary character.
If she be like that I’m gonna guess she’d still have trouble feeding one positive pregnancy test.
I usually just throw them out.

