Smoke is the Slavic enenra ninja who serves the Lin Kuei and was roboticised in the old timeline. No relation to Big Smoke.
Kintaro is the second Shokan champion who picks up the slack after Goro loses. He is not the same as the mythological figure of the same name.
The Other Darrin: Most of the characters had to be played by new actors when half of the original cast left Midway after II due to a royalty dispute.
Liu Kang (Ho Sung Pak in the first two games, Eddie Wong in the third)
Johnny Cage (Daniel Pesina in the first two games, Chris Alexander in Trilogy)
Kitana, Mileena, and Jade (Katalin Zamiar in Mortal Kombat II, Becky Gable in Ultimate)
Sonya Blade (Elizabeth Malecki in the first two games, Keri Hoskins in the third)
Shang Tsung (Ho Sung Pak in the first, Dr. Phillip Ahn in the second, John Turk in the third, Richard Divizio in Mythologies)
The Ninjas (Daniel Pesina in the first two games, John Turk in the third game, Ultimate, and Trilogy)
Stopped Numbering Sequels: The first three sequels were numbered (II, 3, and 4), but every game afterward (when the series no longer had arcade releases) used subtitles instead (although the Deadly Alliance logo does have a huge "V").
Real Life Writes the Plot: The fight scene between Reptile, Johnny Cage, and Liu Kang was added after test audiences were dissatisfied with the other fights in the movie. Linden Ashby wouldn't have been on set.
Throw It In: Liu Kang was supposed to duplicate the acrobatic flips of Sub Zero's down the ramp during the fight, but Robin Shou couldn't pull it off successfully. After a few takes, instead of the acrobatics, he just ran down into the ramp yelling like a maniac. That's the shot that got used.