Well I have a couple, not so much stupid as they came from small kids…
I used to work at a kid’s science museum. While describing the differences between solids, liquids, and gasses to 4th graders, I mentioned how the molecules are packed very tightly in solids (of course with ten of them in the front packed as close to each other as possible for demonstrative purposes.) So I get the question, “Are molecules animals?”
My friend got a better one though. While showing our replica saber-toothed cat skull, complete with huuuuuge, meat-tearing teeth, one child asked, with a purposeful look on his face, “Are saber-tooth cats related to vampires?”
And finally, from an adult… We had a an exhibit of the Ancient Seas complete with a plesiosaur skeleton replica hanging from the ceiling. A woman came in, looking up in awe. She walked from under the head portion all the way down to under the tail and looked puzzled- looked from head to tail to head to tail, then finally asked me,
“Was that really their skeleton?”
Me, thinking she was amazed by the size, “Yes, and that was a youngster!”
The woman said, “Wow kids, the young ones had two heads!” wtf???
During that same exhibit we had a coworker who kept referring to the Cretaceous period as the Crustaceous, which always made me laugh. And no, I never corrected her.
Oh and one more for the road… When I worked there we gave out polished rocks to the kids; little semi-precious things as prizes for completing a puzzle, etc. A mom came up to retrieve one for her son, saw the sign that said “Polished Rocks” and said to her son, “Wow Johnny! Look at how pretty the Polish rocks are! You know your grandma is from Poland!”
I swear I didn’t make any of this up. Anyone who works with kids can tell you! These are all better than the comment I got from a kindergartener my first day of teaching kindergarten music class, “Gee, she sure does have a big butt!”