Prologue is the opening cutscene of Grand Theft Auto: Liberty City Stories, which contains Easter eggs referencing earlier Grand Theft Auto games.
In the opening part of the cutscene, while Toni is walking from the payphone to the taxi, the music that can be heard is actually a remixed version of the Grand Theft Auto III theme tune. It is possible to hear it on the game's official website.
Another Easter egg is the bag that Toni is carrying. It is the exact same suitcase that was carried by CJ in the opening cutscene of Grand Theft Auto: San Andreas. It also features the Rockstar Logo.
GTA- LCS-Mission-01 - Prologue & Slacker