- Acting for Two: In accordance with genre convention, only mods can do this (with one player character each plus any NPCs they may control). Fittingly, prominent NPC the Balladeer and the other two mods' characters are either traditionally double-cast (Hook) or from something where half the other characters are (Eliza).
- Acting in the Dark: Like with other games of this type, players have to actually figure out the cases.
- Cameo Prop: Many of the Merchandise Booth items reference other musicals.
- Cut Song: The second culprit's "Still Alive" couldn't make it to the final case due to how that one went, but was released by the mod plurk.
- Fan Nickname: A few of them are there already.
- Valjean: Bread Dad and French Jesus. These are mentioned in the epilogue.
- Eliza: Founding Mom
- Astarte's Superpowered Evil Side is called "Impostor-chan," "Stabby," or "Genocider Astarte."
- "Billydeer" for the Balladeer became an In-Series Nickname.
- Javert: Law Dad
- The events of the game's unfolding backstory gained the nickname "Round 0."
- "Bad Santa" for King Charlemagne.
- Billy H. and Hans, of all people have become known as Team "Love Made Us Better People."
- Marth Debuted in "Smash Bros.": This can and has introduced players and spectators to a lot of new canons.
- Orphaned Reference: See Cut Song. The execution song still filked "Want You Gone."
- Similarly Named Works: Barring any surprise crossover twists, this game has nothing to do with the musical Curtains, even if that was also a murder mystery.
- What Could Have Been: According to Word of God, endgame was almost completely reworked during and after the penultimate trial to go along with the players' actions. The Balladeer's Laser-Guided Amnesia was inspired by an early IC theory and the ending was originally going to feature a burning Collapsing Lair.
- Working Title: The working title was Curtain's Up in the initial interest check.
Trivia / It's Curtains