A pimp disc is a CD or DVD full of fanfiction, fanart, character info, story info, etc of a specific fandom. They are used to encourage people to join that fandom.
Mary: Anne sent me a pimp disc of 'Prince of Tennis' last night.
Ella: Oh, I've heard of that anime. Is it good?
Mary: Well, the disc had the first episode and some fanfiction, and it looks pretty cool. I think I'll ask for the box set for Christmas.