COUNTLESS times where out and out strangers have glared or spoken to my son (or done the ridiculous "sweet" voice when they're talking to you "through" your child).
My favorite, I've shared a couple times, so I'll make it brief. My son was around 9mo old and I had him in the baby swing at the park. He'd JUST learned to crawl. A mom of a walking toddler was insistent that he go on the "big boy swing", because HER child was only 2 or 3 and couldn't hold on yet.
Lady... he's not even a year old yet, and isn't even walking.
She didn't believe me until later when he was crawling about.
Soooooo many stories like this. "Kicked" out of toddler areas because they thought he was an elementary school kid (not because he was rough, or breaking the rules, PURELY a "This area is for children 4 and under". "He's 3!"... Well... He was over 3' tall at 2, and was 4 feet tall at 4ish/5ish). Thanks GOODNESS his growth slowed down. But at age 9, he's usually mistaken for a 12yo.
I can't tell you how many times people thought he was autistic (because normal healthy 2yo behavior in a kid someone thinks is 4 or 5 looks developmentally off), or how many times people told or insinuated that I should stop babying him. <rolls eyes>. Of course. NO 18 month old wears diapers!!! (We were in size 6 diapers at 18mo)
Conversely, because he's actually "gifted" (rather loathe that term, but hey, whatever. It's a word) that would often make the problem worse.
It's still a struggle, and has been for most of his 9 years. People place expectations on him that are FAR beyond what he's capable of. It's sooooo sad. Because he'll be working really hard on something, or trying his BEST (and doing really well for his real age!) and he gets chastised for it, or looked down upon for not doing "better" for the age they THINK he is!!!