Could a ceiling collapse on them if someone was in a basement during a tornado?

Get into the basement and under a table or something like that.  

LOL Being from California where we have earthquakes not tornadoes, I'm horrified at the idea of going UNDER the house during a natural disaster!  You go outside, away from the shelter, of course!

Happens all the time. It's not just the basement, it's the strongest part of the house, the lower the better. In my house, that would be the bathroom in the basement with four walls close together helping to proved support

Yes, a ceiling or the entire house can collapse into the basement if the house is a direct hit.

The general safety instructions I remember as a kid, when I lived where there were tornadoes, was first the basement, then under a sturdy table. My dad had a model train set up he'd reinforced that we could all get under.

I took a poopy butt stinky diarrhea stinky green diahrea in diaper XD