"A few others:
Metamorpho just wears swim trunks/shorts
Hulk originally wore purple swim trunks, then his tattered purple pants for decades
The Spectre wears just shorts, gloves, and boots (along with his cape/hood, of course)-- the white is his…"
"I was always struck by the similarities between the Atom's costume and that of Menthor (T.H.U.N.D.E.R. Agents). Gil Kane (with George Tuska) drew the first Menthor story, although that doesn't mean he designed the costume -- Wally…"
"I'll end the month with a Jungle Jim cover (#18, 1958). To my mind, Jungle Jim is one of the most inspired names and one of the silliest at the same time. Wikipedia tells us that the jungle gym was invented in 1920, while Jungle Jim…"
"Here's one that always struck me as weird. Why can Ultra Boy only use one superpower at a time? I guess he can't chew gum and walk at the same time. It may make sense if he has a finite amount of some internal energy…"