re: Are “crazy checks” a real thing or just an urban myth?

SSI disability is a real program, and mental retardation, autism, learning disabilities, developmental delays, bipolar, and the like are potential grounds to qualify.

The rule book is thicker than the Bible, and it's not nearly so easy to qualify as people act. You don't just show you have ADHD and get a check. There are other demanding requirements.

They usually send the kids to consulting doctors, psychologists, etc. for assessment, and most of them are quick to call BS on fakery or malingering.

If the kid has an IQ over 70, can tie his shoes, and doesn't shite his pants or bite a teacher too often, he probably won't qualify. That's not straight out of the rules, but you get the picture.