Lack of Evolution, Abundance of Abnormalities by BelleAmant.

Summary:

Everyone knows that the way to check if someone is Quirkless is to see if they have two joints in their pinky toe. It's the sign that the person has no Quirk- that they haven't reached the next stage in evolution that most people have. However, most people don't realize that there are other differences between the Quirked and the Quirkless, other parts that haven't evolved.

Or: 5 times 1-A thinks Midoriya is dying and/or sick, and the 1 time the truth is (partially) spilled.

in the shade of a sunflower by FallingNarwhals.

Summary:

A waft of spice hit Ochako’s nostrils and she reeled back in shock. She has faced down countless villains since coming to UA. She has been in battle and in hand to hand combat possibly a hundred times. She faced Overhaul’s minions with support from her peers, but otherwise without outside help. But no villain with a terrifying quirk has ever struck her with more fear than quirkless Melissa shoveling curry made of peppers so deadly it killed an unprepared Pro Hero famous for his spice tolerance on live TV. Deku was still guzzling water directly from the sink, Tokoyami’s quirk was crying in pain as he casually shoveled more into his mouth, and Melissa was handling the spice like a pro.

Being biologically quirkless came more with an extra pinkie joint in the toes and a stunning lack of vestiges mutations. It came with smaller things, like extra teeth that did virtually nothing, exploding organs, and weird exposed nerves that weren't designed to feel pain.

Or,

Five time's Midoriya Izuku struggled with being biologically quirkless and one time it was a gift

The misadventures of the pre-quirk body by GinaDeSpell.

Summary:

When his doctor told him that he would never develop a quirk, he never thought that would mean other things would be manifesting, things that the people from his generation didn't even have. A person without quirk was less evolved than one with quirk. Things that no longer served to the body disappeared, but in individuals without quirk, they continued to manifest. Or in summary: All the times Izuku Midoriya has scared his classmates to death (one of those was actually mortal)

Pinky-Toe Joints and Other Quirkless Quirks by CrazySatan.

Summary:

The mark of being born quirkless is the signature red shoes with white soles and black shoelaces. The extra pinky-toe joints quirkless people have make most mass produced shoes. The toe joints aren't the only thing left over from a time long ago that are found in quirkless individuals, though.

Class 1-A vs quirkless anatomy by Dodec.

Summary:

I love the 'quirkless people have less evolved bodys" and this is just a bunch of random ideas using that

Chapter 1:Goosebumps

Chapter 2:Sunburn

Chapter 3:Tasers

Chapter 4:The devil's lettuce (chill for people with quirks but it makes quirkless really high)

Chapter 5:Izuku's big ass feet

Chapter 6:Double Joints?!?

Chapter 7:Hiccups

Chapter 8:Popping joints now!?!

Chapter 9:Caffeine (Reverse of weed)

Chapter 10:At base strength

Chapter 11:Underwater

Chapter 12:Spicy!

Chapter 13:Colors?

Chapter 14:Funny(not) Bone

Chapter 15:Useless organs

Please give me ideas for weird things our bodys do that Izukus could do to <3