Wikipedia
Marols or Marollien (also known as Brusselse Sproek, brusseler, brusseleir, brusselair or brusseleer ) was a dialect spoken in Brussels. Essentially it is a Dutch Brabantian dialect incorporating many words of French origin as well as a sprinkling of Spanish dating back to the rule of the Low Countries by the Habsburgs (1519-1713). Its name refers to a district of Brussels called Marollen (Marolles), a neighborhood in the central municipality of Brussels, not far from the Palace of Justice. The district takes its name from the former abbey of the nuns Maria Colentes (Marikollen). It was a working-class neighborhood, though now it has become a fashionable part of the city. Marols is described as "totally indecipherable to the foreigner (which covers everyone not born in the Marolles) which is probably a good thing as it is richly abusive."
The Théâtre Royal de Toone in Brussels puts on puppet and plays in Marols.