Stubby Boardman was the lead singer of a musical group called the The Hobgoblins, who retired in 1980 after having a turnip thrown at his ear during a concert in Little Norton at the Church Hall. He and Doris Purkiss appear to be in a relationship.
It was said by The Quibbler in 1995 that he was in fact Sirius Black in disguise, based on the word of Purkiss, who claimed that she was having a romantic dinner with him on the night he supposedly murdered Peter Pettigrew and twelve Muggles. In 1996, The Quibbler claimed this person was Mina Lima in disguise. Both claims were false.
A boardman is a man who perambulates the streets carrying an advertising-board; a sandwich-man.