The Popeye Myth is that spinach contains lots of iron.
According to Brainpickings website
Back in 1870, Erich Von Wolf , a German chemist, examined the amount of iron within spinach, among many other green vegetables. In recording his findings, he accidentally misplaced a decimal point when transcribing data from his notebook, changing the iron content in spinach from 3.5 milligrams of iron in a 100-gram serving of spinach, to 35 milligrams. It was corrected in 1937, but too late the myth was well established.
This study inspired the Popeye Cartoon character who gets colossal strength eating cans of spinach.
Unfortunately, it was just a maths blooper. The good news is that:
Popeye Myth Busted.
Spinach does not have that much more iron than other vegetables.