For this you need the saves on your memory card from the games mentioned in requirements. From the main menu select "Secrets shop", then scan for secret characters. You should have some of new characters: Ratchet, Jak 1, Jak 2 and Jak 3! have fun racing...
more
1. Turn on and load a Daxter save file.
2.Connect the PSP to the PS2 via USB mode
3. At the secrets menu in both Jak X and Daxter select "Scan for secret characters" and "Connect to Jak X" respectively.
4.THere should be characters unlocked in Jak...
more