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Mortal Kombat Part 2 - Did You Know Gaming? Feat. Two Best Friends Play
Mortal Kombat - Did You Know Gaming? Feat. Two Best Friends Play
 
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There are a lot of unused sprites of Motaro left over in the game's memory, including:

• Motaro raising up his front legs.
• Motaro doing his teleport move.
• Motaro performing an arm lift as if he were going to throw the opponent over his head.
• Motaro raising his arm, along with moving mouth sprites that suggests this would be some sort of taunt.

There is also an unused win screen for him that would not show up until Mortal Kombat Trilogy. This evidence suggests that Motaro was probably going to be a playable character at one point.
Contributed by MeleeWaluigi
Because Sheeva has four arms, a unique four-armed skeleton sprite is stored in the game's memory but is never actually used in-game. This was likely meant to be used for Kano's skeleton rip Fatality.
Contributed by MeleeWaluigi
Shao Kahn was voiced by Steve Ritchie, who was working at Williams Electronics as a pinball and video game designer at the time.
A large number of unused items in the game's code suggests that the ninja characters were originally planned to appear in the game. These include an animality animation for Ermac, a friendship animation for Classic Sub-Zero, unused win text for Scorpion, and a debug menu with references to Sub-Zero and Smoke.
Contributed by Dazz
By performing Nightwolf's Friendship, he will transform into Raiden with a Mortal Kombat II arcade cabinet. He also says "I've never seen a Kano transformation," which is referring to the rumors that Shang Tsung could transform into the missing Kano in Mortal Kombat II.
Contributed by gamemaster1991
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Viewing the full model of the bank from the Street stage shows carvings referencing Pac-Man.
Contributed by DeerBoarDude
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Noob Saibot's sprite in Mortal Kombat 3 is actually a blackened Kano sprite. He uses Kano's combo moves but none of his special moves. The reason for this is that there were no ninja sprites in the game.
Contributed by Shinitenshi
Cyrax and Sektor were named Mustard and Ketchup respectively during development until they were finally given names.
Contributed by Shinitenshi