Prop Recycling: The opening cutscene uses Sandover Village from the first game, albeit slightly visually modified.
What Could Have Been: As you can see from the Toonami promo for this game, Jak was originally supposed to have the horns he has in Dark Jak mode throughout the entire game. For some reason, this was scrapped from the final game, but there is a glitch where if you walk right near the mirror in Krew's bar, you'll see the horns flicker in and out.
According to one magazine, there was a side mission where Jak would compete with some guys in a Jet-Board competition. This was ultimately scrapped from the final game.