Paprium [Model T-574120]

Obj viewer:
On options screen Highlight "BOF naming" and input: Start, X, X, A, Y, C

Megawire 4.0 screen:
On options screen Highlight "BOF naming" and input: Start(x4), C, C

3-player game!:
On map screen before character select; A(x3), Up(x3), Down(x3)

Stage BLOCK 888:
After leaving the first room, if you go to the left you can skip the whole level and go straight to the boss area. You'll hear Showtime yell Sissy!. This only works after your first playthrough.

Stage BION MART:
There is a shop with a ton of 50% stickers plastered all over it. Break the storefront to access a bonus room. The room also seems to be the only place in the game where the song 1988 Commercial plays!

Stage ROOF-TOP:
There is a pillar marked with an X which when hit will drop a ladder, taking you to an alternate section.

Stage REFORMATORY:
Get to the first area that has a pillar in the middle of the arena, then jump-kick the upper-left corner of the screen. You'll hear a breaking sound. Hit that spot for a while and you'll hear Showtime yell HEY and then you'll be transported to an area based on the second level of Streets of Rage (Inner City), complete with Galsia enemies!

Stage CENTRAL PARK:
There is a breakable brick wall that will take you to a brief forest segment.

Stage THE DOCKS:
Location is signaled by Ba Ba's little pink drone zooming across the top of the screen. A breakable door will take you to an elevator leading to the Mid-Levels path. This is also where you can fight/unlock Ba Ba. (After unlocking Ba Ba, the drone is replaced with a Mojo/Rutubo)

Stage AQUAWORLD:
There is a small piece of glass marked with an X that can be broken to take you to a short lower area where a tied up enemy can be found.

Stage POWDER-ZONE:
There is a breakable lock just before the boss area, next to a throwable bust. Break this to go to an alternate path. This is also where you can fight/unlock L.Ektra.

Stage DEEP STORAGE:
At the very beginning of the stage, jump-kick the upper-left corner of the screen. You'll hear a breaking sound. Hit that spot for a while and you'll hear Showtime yell HEY and then you'll be transported to an area based on the desert level of Golden Axe III.

Good ending:
Complete the game with all three thronable paths (Mid-Levels, Low Levels and Underground) paths throned, and with all 3 missions completed on each.

Bad ending:
Complete the game with only the Low Levels and Underground paths throned, with all 3 missions completed on both.

Alternate Character Colors:
Complete the game after playing the save for more than 1E0 minutes (8 hours). Then, press X, Y, or Z on the character select screen to use the alternate colors.

Arena Mode:
Complete the game with the Bad Ending.

Boom Box (sound test):
Complete Original Mode with more than 160000 points, or press Up-Up-Down-Down-Left-Right-Left-Right-B-B on the main menu (a sound effect will play to confirm code entry). The Boom Box is in the Options menu, labelled '?'.

Paprium Difficulty:
Complete the game on Very Hard.

KTV Member Card:
Complete the Low Levels path in Original Mode. The boss, Pang, will give you his KTV Member Card. This is needed to access the last levels of the game (THE VAULT, SANOPHIX LABS, THE SOLARIUM).

Soft reset:
You can soft reset the game by pausing & pressing A+B+C+Start.

Bonus screens when holding buttons at boot:
Start: Speeds up game startup
A: Displays a image of a scum vandalizing an Air France poster. This is likely a reference to Fonzie's dislike of Air France due to them losing a development kit.
B: Displays your Datenmeister's serial number at the top of the Sanophix terminal screen.
C: Displays an image of two scums ogling an extremely scaled up NoName robot.