OPP still puzzles me though, why would R.M.C. (which I believe painted the picture) sign it with OPP?

The title is an acronym for “other people’s property”; when the song asks if the listener is “down with O.P.P.”, it's asking if he/she is willing to have sexual relations with a person who is known to already have a significant other. Lead rapper Treach coyly obscures the meaning of the second “P” (which is meant to refer to either “pussy” or “penis”) using euphemisms throughout the song saying – instead of pussy – that it is “another way to call a cat a kitten” or – instead of penis – a “five-letter word rhyming with cleanness or meanness.” In the lyrics following, the rap defines the second “P” as “property” to “do it sorta properly.”