The word "fuck" and its derivatives are used three hundred and sixty-five times, not counting the soundtrack or random NPC interactions.
If you go north of the Military Base in the desert, you can find a body dump.
The mission "Saint Mark's Bistro" has CJ travel to Liberty City to deal with the Forellis at the restaurant of the same name. The restaurant exterior is faithfully remodelled from Grand Theft Auto III (2001).
The character Lance "Ryder" Wilson is modelled after late rapper Eazy-E, the founding member of N.W.A. Music from N.W.A. and Eazy-E is included in the soundtrack.
In the graveyard in San Andreas, there is a crypt the player can enter. Inside, there's a chair, a television set, and some old pizza boxes. This is possibly a reference to Buffy the Vampire Slayer (1997).