Back in the macho '70s, real men didn't wear underwear.
These days, "onesies" are mostly worn as pajamas, mostly by men with tribal tattoos.
"Man Zone Steam Onesie"
Via: undergear.com
Or by confused guys like this. Not very practical, what with the airiness.
Via: guillehg.tumblr.com
But, back in the Decade of Unending Hot Hairy Sex, men wore onsies to work, dinner, and disco.
GOD, that Gingham design oozes man musk.
Image — and inspiration for this post — via Dangerous Minds.
Perfect for Night Fever...
"Zipper front (careful), drop seat..."