After you kill the drug dealers in the "Shadow" mission for Little Jacob, leave the room and go back the way you came. On the wall just before you go down the stairs you will see graffiti which has the name of every previous Grand Theft Auto protagonist on the wall; Claude from Grand Theft Auto 3, Tommy from Grand Theft Auto: Vice City, Carl from Grand Theft Auto: San Andreas, Tony Cipriani from Grand Theft Auto: Liberty City Stories, and Victor Vance from Grand Theft Auto: Vice City Stories. The text says things like "Victor - never forget you / always remember you bro", "RIP Claude", "RIP Toni", "remember Tommy - u r still my hero", "Carl I love you RIP everyone miss you", "RIP Vic".