- Beam Me Up, Scotty!: Many people claim that Zak Gramarye hid the final page of Magnifi's diary that would have cleared his name and prevented Phoenix from getting disbarred for presenting forged evidence because presenting it would have caused Valant to become the prime suspect instead. Zak never says this when meeting with Phoenix at the Borscht Bowl Club; in fact, he reacts with surprise when told that Valant was suspected of the murder.
- Sequel First: In Europe, this game came out before Phoenix Wright: Ace Attorney - Trials and Tribulations.
- Technology Marches On: In Case 4, the murder victim is poisoned by licking the back of a stamp bought in 2018. While the fact that he only used paper mail as correspondence is noted in-universe to be unusually old-fashioned, modern stamps are self-adhesive and don't need to be licked before use.
- What Could Have Been:
- The game was originally supposed to be a soft reboot of the franchise, with Phoenix Wright not appearing. This is why almost none of the cast of the original trilogy appears. However, due to a mandate from Capcom, Phoenix Wright remained a main character in the series.
- The development team considered making the game with a fully 3D engine, but determined that the Nintendo DS wasn't powerful enough to deliver the results they wanted, causing them to stick with sprite graphics. It wouldn't be until the release of the Nintendo 3DS that they were able to go fully polygonal.
- Trucy was originally conceived of as a trainee ninja, before being turned into a young magician.
- While it was always planned for Kristoph Gavin to be exposed as a murderer in the fourth case, had Phoenix's inclusion not been forced on the development team, then Kristoph would have remained as Apollo's mentor throughout the storyline. Turnabout Trump would therefore have been a much more standard-issue first case, with Apollo defending a different client (possibly Trucy), and Olga Orly turning out to be the murderer.
- Wendy Oldbag was originally supposed to appear in the game, as she appeared in one of the game's trailers, but she was cut from the final version of the game. However, in Turnabout Corner an unnamed but suspiciously similar old lady can be seen fighting with a police officer about getting into the closed park for her daily walk.
- The game's writer, Shu Takumi, had the idea for Turnabout Corner in 1995, long before the Ace Attorney series began. He brought the concept back for this game.
Trivia / Apollo Justice: Ace Attorney