Mayo Kaan, born and raised in Revere (he eventually became head lifeguard at Revere Beach), went to his grave in 2002 proclaiming he was the male model on which Superman creators Jerry Siegel and Joe Shuster based the Man of Steel (literally - click the link to see his tombstone).
Siegel and Shuster, both from Cleveland, always denied ever knowing Kaan, let alone traveling from Cleveland to Massachusetts to employ him as a model. Kaan, who went on to open a gym, took out ads in 1997 to sell autographed photos of himself in a sort of Superman uniform - but unfortunately for him, one of the photos which he claimed proved his case showed him at the Hatch Shell, which wasn't built until after Superman had burst on the scene.
A few years ago, Steven Brooks took a look at Kaan's claims and mostly debunked them - yes, Kaan eventually posted as Superman in the Boston area (with a homemade Superman suit), but, no, he wasn't the actual man behind the hero. Brooks updated his article a couple days ago with a copy of a 1942 Globe article about Kaan, which seems to indicate Kaan first donned his uniform to help promote the sale of war bonds - and that a generous explanation might be that Kaan got his own history confused, that maybe he did audition for some early Superman movies.
H/t Harry McCracken.