For me it is the fact that our blood contains iron. I earlier used to believe the word stood for some ‘organic element’ since I couldn’t accept we had metal flowing through our supposed carbon-based bodies, till I realized that is where the taste and smell of blood comes from.
To piggy back on your “bizarre fact”, the same type of iron can be found added to cereal.
I remember several times in school we’d do a science demonstration where we’d smash up Cheerio (or a knock off) brand ceral, mix the powder with water and slowly drag a magnet through the slurry. Every time the magnet would be pulled out of the mix, there’d be more and more tiny iron bits.
We did the same but with Special K in a blender, and held a magnet to the side of the blender’s cup.