In Captain America: The First Avenger, HYDRA head Johann Schmidt tested a version of Abraham Erskine’s Super Soldier Serum on himself.
However, the effects saw the Nazi become terribly disfigured and gain the name Red Skull.
Skinny little Steve Rogers was injected with the serum too, but the results were very successful, as he became the super soldier of the Avengers we know today.
But now a popular new fan theory has argued why the Red Skull was deformed by the serum but Captain America wasn’t.
Reddit user rafael-a wrote: “Bacteria is the answer.
“In the scene of the transformation of skinny Steve Rogers into big buff Captain America there is a small joke where Erskine injects him [with] penicillin beforehand.