Downhill Snow

Hidden Characters
Beat the game on Hard to unlock two hidden characters.
Mirror Mode
Beat the game on Normal. Mirrored tracks are selectable in Practice.
Extra Costumes
Beat Scenario Mode with each of the characters.

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 Dracula X

Inverted Castle
If you defeat the pssessed Richter Belmont in Dracula's Keep, you'll see the ending. But what you may not realize is that this is the bad ending, and you you've only seen half the game. To get to the real ending, read on:
First, make sure you've gotten both rings from Maria. The first you receive after defeating the Succubus in the 'Nightmare' stage. The second is past the hall with all the spikes in the Cathedral.
Equip both rings at once in the room with the big clock, and the floor will open. Down in this lair, Maria is waiting for you once again. She'll give you a vital piece of information.
Once all this is done, then go to Dracula's Keep and meet Richter. He'll attack you, but you will now be able to see a green orb floating above him. Attack the orb, but don't kill Richter. After a bit of attacking, the orb will break open, revealing everyone's favorite loathesome 18th/19th century warlock, Shaft.
This also breaks Shaft's spell, freeing Richter from the spirit of Dracula. Alucard will tell Richter and Maria to escape while they can as the clouds swirl and open up, revealing a mirror-image of the Evil Castle. Shaft escapes into the Inverted Castle, and of course, it's Alucard's duty to chase after him.
But just when you think you know the layout already, you find some crucial elements of the castle have been rearranged, it's stocked with bigger and badder enemies, and even the music has changed.

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 Dragon Ball Final Bout

Goku 4 Encarnation of Saiya
In the title screen, press Right, Left, Down, Up, Right, Left, Down, Up, Triangle, Triangle, Triangle, Triangle, Triangle, X, X, X, X, X, X, X, X, X.
Play as SS Gotenks
Beat the game on Hard 9 times with Regular Trunks and without dying. Now, go to Trunks and press Select(9x).
Bonus Fighters
At the Title screen, press Right, Left, Down, Up, Right, Left, Down, Up. If done correctly, you will hear a sound.
Wire Frame Characters
While choosing your fighter, hold Select.
Alternate Costumes
In Two-Player or Training Mode and when choosing your fighter, press Square + X + Circle.
Sound Test
At the Title screen, press L1, L2, R1, R2, Start. Then, after choosing a song, press Select to view the lyrics and additional song info.

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 Dragon Ball GT

Play as Level 4 Goku
At the title screen, press Right, Left, Down, Up, Right, Left, Down, Up. If done correctly, you should hear a tone. Next, press Triangle 5 times, then Square 9 times. You'll hear another tone if done correctly.
Super Saiyajins
At the title screen, press Right, Left, Down, Up, Right, Left, Down, Up

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 Dragon Ball Z Ultimate Battle 22

Extra Characters
At the title screen, press Down, X, Up, Triangle, Left, L1, Right, R1. The game will load the anime for the 5 extra characters, and the title will change to Ultimate Battle 27.