When somebody (usually/hopefully a girl) wears a bunch of different bracelets on the same arm, sometimes using many bright colors or different materials/metals is called an arm party. The more the merrier!

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.