Insulting phrase used to describe someone who acts like someone or something else, usually in order to fit in. A fake person.
Wintston used to play golf and wear sweater vests. But ever since he moved to the ghetto he's turned into a real chocolate milk napkin. Lately he's been selling drugs, spending all his money on fresh kicks, and listening to lil wayne.
Two months ago Margaret saw Danielle's grandpa take a shit in church. Now Margaret does it every sunday. What a wrinkly old milk napkin.