Winston Churchill invented an adult romper suit and then wore it everywhere during World War II.

When I think of Winston Churchill, the first words that come to mind are not “fashion icon.” And yet he had a one-piece garment custom-made for his personal use, and that garment became something of a wartime fashion statement.
This outfit was popularly known as a “siren suit” (although that was not Churchill’s name for his original suit). It looks much like a onesie, a romper suit, a jumpsuit, or overalls, with a zipper in the front and – sometimes – a buttoned-up opening in the rear. The intention behind such clothing was purely speed. When the air raid sirens started calling, you needed to get dressed and down to the bomb shelter as quickly as possible.
Churchill directed the men’s tailors / shirt-makers Turnbull & Asser to make him a siren suit. And then another, and another. And one in pinstripe. And one in green velvet. And he wore them out to official functions, as rumour has it even offending Stalin by wearing it to the Kremlin.
The siren suit became a moderately popular piece of wartime apparel, worn by men, women and children as they went to the shelters. Its use thankfully died out after the war, although Churchill kept his and would later pose for portraits while wearing them. He did rather lean on his wartime gravitas in later life, no?