At this point my little people have not eaten in over 24 hours, and their "fed" bars are still super high. Is this normal, do they not need to eat multiple times each day (or even ONCE a day)? Or is this a bug?

I'm not sure, I checked mine this morning and they had full bars and then have been playing since and then had to go to work for a while and then this evening mine have had full bars that haven't gone down much, I've not fed them at all today, but they do seem to drink a lot of water, maybe mine are getting it that way, tho my food does seem to be going down. Maybe they are invisible eaters?
But yeah, I've found pretty much the same as you.

Hmm my food isn't going down and they don't drink any water. But the bars haven't gone down in 24 hours. So weird!

They sneak snacks when you're not looking. Seriously, if there's food in the fridge, you don't need to worry about them starving.

Okay! That makes my life easier, then! Thank you