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.
Not exactly bizarre, but it’s fun to learn that the delicious fragrance of shrimps and crabs when cooked comes from chitin, and chitin is also why sautéed mushrooms smell/taste like shrimps.
And since fungi are mostly chitin, plants have evolved defenses against fungi by producing enzymes that destroy chitin, which is how some plants eventually evolved the ability to digest insects.
EDIT: a previous version of this post mistakenly confused chitin with keratin (which our fingernails are made of). Thanks to sndrtj for the correction!
Chitin is not produced by mammals.
Fingernails are composed primarily out of keratin (same as hair and skin).
Oops! I stand corrected.
Huh. Oddly I am allergic to shrimp and lobster, but love mushrooms. To me they don’t smell the same though. Though this fact probably explains why veg oyster sauce is mushrooms.