 The character of "Bubbles", played by Andre Royo (qv), was largely  based on a real Baltimore drug addict and police informant who went  by that name. The real Bubbles, who would slur his speech much more  than the fictional character, first started working with the cops  near the early 1960s after being arrested for a burglary. He spent  the next few decades as an informant, leading to the arrest of  several hundred felons and getting paid at least $50 for each one  caught. His photographic memory and ability to blend into the scene  made him one of the best in the city. Eventually he would start  using the hat method portrayed on the series, where he acted as if  he was selling hats and would place one of a certain color on the  head of those the police should arrest.