A frilly-looking sort of skirt, made of tulle and worn by ballerinas and cool people. One can tell when it is worn by a ballerina because the person in question will usually also be wearing some form of dance shoe and have their hair up in a strict bun. When a cool person wears a tutu, one can tell because others are always gazing upon them in unabashed admiration and desire. Cool people in tutus can often (but not always) be found fighting crime, assassinating terrorists, and helping little old ladies cross the street.
Ballerina: Look at me dancing around in my little tutu!
John: Emma is wearing a tutu. She's not a ballerina, so that means she must be a cool person. I wish I had a tutu.
Passerby: Don't we all.
An outfit donned by either losers, freaks, or Peter Parker. One can tell if the costume is worn by a loser or a freak, as they will have attached false legs to it to simulate the eight legs of an arachnid. On the other hand, when the costume is worn by Peter Parker, he then becomes Spider-Man. It will be very obvious when this happens because of the undoubted element of badass appeal, and the fact that the wearer will most likely be fighting crime and/or swinging from building.
John: I'm wearing a Spider Costume! Look at my eight legs!
Passerby: You are a loser/freak.
Peter Parker: Oh no! A bank heist! I must put on my Spider Costume and stop it!
Passerby: You are undoubtedly badass.