Johnny Cage is based on Jean-Claude Van Damme. The creators wanted Van Damme to be in the first Mortal Kombat, but Van Damme was unable to due to his busy work schedule. Johnny Cage's clothes in this game are almost identical to the clothes Van Damme wore in the last match in the movie "Bloodsport", and his Split Punch is taken directly from a move done by Van Damme in Bloodsport. Cage's Nutcracker Split Punch was also inspired by Bloodsport.

In the audit menu of the arcade version, there is a useless row of text that says "ERMACS" (which stands for Error Macros) and is listed under "Reptile Battles." Because of this, players thought that Ermac was a hidden boss like Reptile. Ermac became a running joke for the developers, so much so that they even made him a real character for Ultimate Mortal Kombat 3, with his BIO saying he was hiding in the first Mortal Kombat.

In most versions of the game, there's a way to fight a secret character called Reptile. Deciphering the clues that are given in between random matches will lead the player to finish a fight on The Pit stage with two perfect rounds, without blocking, and when shadows pass over the moon. If this is done, the next round will be with Reptile, who has a combination of Sub-Zero and Scorpion's move sets, as well as displaying Scorpion's name.

According to Guinness World Records, Reptile is certified as the first ever secret character in a fighting game.

Mortal Kombat is partly responsible for the creation of the ESRB; mostly due to Sub-Zero's head rip Fatality being so violent.

Raiden's look and moves were based on Lightning from the movie Big Trouble in Little China.

Originally, Jax was going to be in the game, going under the name Kurtis Stryker. He was later dropped and replaced with Sonya Blade (who also adopting Jax's backstory) when Ed Boon wanted to add a female player to the then all male cast. Jax would later be made into a character for Mortal Kombat II, where he was made into Sonya's partner. The name Kurtis Stryker was later given to a police officer in Mortal Kombat 3.

In the games data is an unused message, which seems to greet a number of people. This is likely a sort of "Special Thanks" list that is never visible in the game.

Shang Tsung originally had a fatality in which he would behead his opponent with his sword. The sprites for this are still in the game's data.

There is a sprite of Johnny Cage doing some sort of flip or flip kick left in the game. He does have a similar move in Mortal Kombat: Deadly Alliance as part of his Karate fighting style, and in Mortal Kombat (2011) as a special move. It's possible this was meant as a special move or Fatality.

On The Pit stage, there is a 1 in 30 chance that a secret game over screen will show up. The Game Over screen pans from The Pit stage down to the Pit Bottom stage, showcasing multiple impaled bodies on the spikes on the way down.

In the very early stages in development, Sub-Zero was called Tundra which was later used as the younger Sub-Zero's initial code-name in Mortal Kombat (2011), Liu Kang was called Minamoto Yo Shin Soo, a character from Japanese mythology which was changed because Ed Boon "just couldn't deal with the name", Johnny Cage was named Michael Grimm, and Goro was called Rokuro, another character from Japanese mythology.

There are several unused sprites in game's memory:

• Goro turning to stone and breaking. This was possibly meant to be used as a dying animation.
• Johnny Cage flipping backwards in the air. He has a similar move in Mortal Kombat: Deadly Alliance and in Mortal Kombat (2011) as a special move.
• Three sprites of Shang Tsung. One is of Shang Tsung laughing, which may have been intended as a win taunt. Another is of Shang Tsung clapping, which may have been intended for the background of the Throne Room stage. Lastly, there is one where he actually uses his sword during combat. Shang Tsung was also originally meant to have a Fatality where he beheaded his opponent.

On September 20, 2008, Brandon DiCamillo of Jackass fame broke the arcade world record on Mortal Kombat with a score of 10,226,500. His record was then beaten on May 2, 2009 by Isaiah TriForce M. Johnson, and DiCamillo's score is currently ranked 3rd overall.

When Mortal Kombat was first tested in arcades, creators Ed Boon and John Tobias never expected anyone to find its fatalities. In an interview, however, Ed Boon said they were discovered by a 12 year old boy on the very first day it was in arcades, and spoke of how the boy spent the rest of the day trying to convince his friends of their existence.

In Japan, the game has been renamed to 'Mortal Kombat: Legends of the Advent God Fist'.

During the early stages of development, lead artist John Tobias had the idea to rotoscope over the motion captured footage of the characters, though the idea was dropped due to time constraints.

Sub-Zero's Fatality was inspired by the scene in Predator (1987) in which the Predator rips out the spine of his victim.

During development, the team had made extra sprite animations, such as both characters walking onto the screen and bowing before the match. But the animations could not be used because of hardware limitations.