The Understudy

This is a core premise for an Inform 7 game, entered into SeedComp 2023 (https://seedcomp.org/)

The introductory text:

"Whoops.

"You agreed to be an understudy for FILL_IN because they have, literally, never been sick a day in their life.  And, you suppose, they still haven't.  And normally, getting trampled by a rogue capybara still wouldn't dissuade them from performing in FILL_IN as FILL_IN, literally their favorite part in FILL_IN's entire oeuvre.  But FILL_IN the director apparently didn't think pushing a comatose patient on stage would do much for the audience's enjoyment, so here you are.

"And normally, you'd be fine with this; you've understudied a lot.  But FILL_IN?  There was no way they weren't going to be here.  So you... never actually learned your part.  Or read the play, really.

"But!  You have excellent improv skills, a keen sense of story and theater, a (generally) excellent cast to work with, and an uncanny ability to fully inhabit the characters you portray.  You got this."

The core idea is that the player can ENTER CHARACTER and BREAK CHARACTER to see their surroundings either as they are in real life, or as they are in the world of the play.  Both may contain vital clues as to what they're supposed to do next.