Marcos Mouse is the main antagonist of the Busy World of Richard Scarry segment "Cucumber in Rio." He is a mouse who has cheated to win a gold medal by wearing one particular Carnival costume (including boots), and stealing everyone else's and hiding them. This made the mayor of Rio declare cancellation of the parade and the costume contest, but Marcos decides otherwise, and gets a medal, much to the crowd's dismay and that of the two photographer-reporters Cucumber and Pickles. When the two reporters ask for permission to ask him a few questions, he steals a float in which he hides the costumes he stole. When they catch him and interrogate him, he reveals that he "borrowed" them because his costumes are beautiful, but because of his small size, he wasn't noticed. When he was accused of cheating, he vows to give the costumes back before it is too late, so Cucumber, Pickles, and Marcos go back to the angry crowd who think Pickles and Cucumber are on Marcos's side (technically, they are right in one way, but not in the way they think). Marcos apologizes and requests that someone else get the medal. When they give back the costumes, they get worn by the wrong performers, so Marcos, remembering who wears which, makes up for that by giving each one the right costume. Finally forgiven by the Mayor, he is awarded by the mayor who vows to make a category for smallest size. Again, because of his size, Marcos has trouble wearing it, so he falls off the float trying to carry it.