Marols or Marollien (also known as brusseleer, brusselair or brusseleir) is a virtually extinct dialect spoken in Brussels. Essentially it is a heavily Frenchified Brabant-Dutch dialect additionally incorporating a sprinkle 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 south-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."
There is a dispute and confusion about the meaning of Marols, which many consider to be a neighborhood jargon distinct from a larger Brussels Dutch dialect, while others use the term "Marols" as an overarching substitute term for that citywide dialect. According to Jeanine Treffers-Daller, "the dialect has a tremendous prestige and a lot of myths are doing the rounds."
If you ask ten Brusselers what "Marollien" is, you get ten different answers. For some people it is French contaminated by Flemish and spoken in the neighborhood of the rue Haute and the rue Blaes, whereas for others it is Frenchified Flemish. Still others say that it is a vernacular variety of French, spoken in the whole city, etc., etc. Marollien, however, is exceptional if not unique, because it is a double language. In fact it is not between the germanic and romance languages, it is both.-- Jacques Pohl, 1953, 
An example of Marols is:
Na mooie ni paaze da'k ee da poèzeke em zitte deklameire / Allien mo vè aile t'amuzeire / Neineie... ik em aile wille demonsteire / Dat as er zain dee uile me konviksen e stuk in uilen uur drinke. / Dat da ni seulement en allien es vè te drinke.-- In Standard Dutch: Nu moet je niet denken dat ik hier dat gedichtje heb zitten voordragen / Alleen maar om jullie te vermaken / Neenee... ik heb jullie willen tonen / Dat als er [mensen] zijn die jullie met overtuiging een stuk in jullie haar drinken. / Dat dat niet louter en alleen is om te drinken.
For the popular comic series The Adventures of Tintin, the Belgian author Hergé modeled his fictional languages Syldavian and Bordurian on Marols, and modeled many other personal and place-names in his works on the dialect (e.g. the city of Khemkhâh in the fictional Middle Eastern country of Khemed comes from the Marols phrase for "I'm cold"). Bordurian, for example, has as one of its words the Marols-based "mänhir", meaning "mister" (cf. Dutch "mijnheer"). In the original French, the fictional Arumbaya language of San Theodoros is another incarnation of Marols.