All Working Vampire: Darkstalkers Collection Cheats - Playstation 2

Play as Another Donovan and and another Phobos
These 2 characters can be played in Vampire Savior (secret version), Vampire Savior 2 and Vampire Hunter 2:

Another Donovan - At character select screen, highlight Donovan, hold [Start] and prees any attack button.
Another Phobos - At character select screen, highlight Phobos, hold [Start] and press any attack button.

Secret characters - Oboro/Shin Bishamon & Alternate Gallon
Shin Bishamon can be played on Vampire Savior, Vampire Hunter 2 and Vampire Savior 2 (normal & secret versions) Alternate Gallon can only be played on Vampire Savior (normal/secret), Vampire Hunter2 (secret) and secret Vampire Savior 2 (secret):

Play as alternate Gallon - At charcter select screen, highlight Gallon, press and hold [Start], then press [L1] (3 punches) or [L2] (3 kicks).
Play as Oboro/Shin Bishamon - At the character select screen, highlight Bishamon, press and hold [Start], then press any [Punch] or [Kick] button.

Secret Option
It's available in the 5 games (Vampire, Vampire Hunter, Vampire Savior, Vampire Hunter 2 and Vampire Savior 2). In the option screen highlight "game option" and press and hold [L1]+[R1], then press [Circle] to enter on Secret Options screen.