A person predisposed to living in a fantasy-like state which leads to acting inappropriately in public, especially owing to drug use or flamboyant, self-indulgent, geeky avocations.
Something which is pointless and overly thought-out or indulgent.
Often used in conjunction with the word "real" as a qualifier to indicate an extreme case where a person feels a need to attract negative attention to themselves, but by doing so, they attempt to ingratiate or force the identification of themselves to the small target audience that the attribute, mannerism or activity is intended for.
Annette's Vulcan ears make her look like a real brass cupcake.
The bar on the next street over must be a gay bar, its filled with brass cupcakes.
The gay guy standing in front of the bar must be a real brass cupcake wearing ass-less leather chaps like that.
When you find a party with people on shrooms, you'll find a lot of brass cupcakes trying to light things on fire.