Acting for Two: Richard Divizio as Kano and Kabal, Sal Divita as Nightwolf and the robot ninjas, and John Turk as Shang Tsung and Sub-Zero. John Turk and Becky Gable both played all the masked ninjas in Ultimate as well.
Approval of God: Lia Montelongo (Sindel) and Kerri Hoskins (Sonya) are huge supporters of fan art and tributes to their MK3 appearance and will often promote said fan works on their social media accounts.
Ascended Fanon: Ermac's name was originally a bit of misunderstood text on a debug screen in MK. Fans believed he was going to be a playable character. Midway took the playable bit and canonized it.
The Other Darrin: Only half of the cast from the previous two games returned, namely Richard Divizio (Kano and Baraka), John Parrish (Jax), Tony Marquez (Kung Lao) and Brian Glynn (Shao Kahn), which led to the other returning characters being played by new actors. Ho Sung Pak (Liu Kang) and Elizabeth Malecki (Sonya Blade) were replaced by Eddie Wong and Kerri Hoskins respectively, while John Turk replaced both, Dan Pesina (as Sub-Zero) and Philip Ahn (as Shang Tsung).
John Turk eventually got to play all the other masked ninjas in Ultimate (replacing Pesina again) alongside Becky Gable, who replaced Katalin Zamiar as Kitana and the other female ninjas.
Chris Alexander was brought in to replace Dan Pesina as Johnny Cage in Trilogy, who was one of the few characters needed to fill the entire roster from the first three entries. Averted by Carlos Pesina, whose character Raiden was left out in MK3 and Ultimate, but brought back in Trilogy with the same sprite set used in MK2 (except for the all-new running animation); same as Baraka, who had been played by Richard Divizio and, therefore, came back with his MKII sprites intact, plus a run animation and a new move.
This is also the reason why only four characters (the aforementioned Kano, Jax, Kung Lao and Raiden) have "past" versions of themselves available in the Playstation and Saturn versions.
Romance on the Set: With Lia Montelongo (Sindel) and Brian Glynn (Shao Kahn), who dated until 2001. It may influenced in the fake marriage between the two characters.
Updated Re-release: Ultimate Mortal Kombat 3 is Midway's apology for not including Scorpion in the original Mortal Kombat 3. As it's the only version of the game to have been included in the Arcade Kollection re-release, it's widely considered the definitive version of Mortal Kombat 3.
Chameleon was supposed to be in the console versions of Ultimate, but was unfinished due to time constraints. Code of him can be still found in the games.
Before they were named, Sektor and Cyrax were called Ketchup and Mustard by the team. Sindel's working name can be seen as "Muchacha" in pre-release screenshots.
Midway was going to release an HD version of Ultimate Mortal Kombat 3, with new motion capture actors and updated graphics, but said project was cancelled by Warner Bros. when they had acquired the company. Also notable is the fact that Elizabeth Malecki was going to reprise her role as Sonya Blade, after years of absence from the franchise.
Working Title: According to an old prototype, Trilogy was originally going to be called Mortal Kombat Kronicles.