Cheat Menu
Go to the options screen and highlight Continue. Now Hold Low Kick + Block until you hear the word Outstanding being said once. The cheat menu should now appear.

Play As Goro
Complete the game with Shinnok. Change Shinnok's costume (hold start and any other button to rotate the screen twice) and select the invisible icon at the bottom of the character selection screen. Highlight Shinnok's icon (press up, up, up, left) then press and hold Run + Block.

Play As Noob Saibot
Complete the game with Reiko. Go into versus mode and enter in 012 012 for the Kombat code. Now Exit the match and enter the character selection screen. Select the invisible icon at the bottom of the screen and highlight Reiko's icon (Press Up Up Left), then press and hold Run + Block.

Glitches:

Missing Text
Defeat Shinnok (or your first opponent if you're using the Endings cheat), then immediately press Start and choose Quit Match as the spiral animation plays. After the sound effect stops, you will return to a text-less main menu. Begin a new game and most of the text (wins, round #, etc.) will be missing until you close the program or beat the game again and go through the credits.