Favorite twists in theatre

What are some of the best twists/reveals in plays or musicals to you? Naturally, spoilers ahead!

I personally love how in August Osage County the reveal of the cousin relationship turns out to be actually brother/sister then more shockingly, Violet knew all along.

My favorite twists have to be in Deathtrap, unless we're going to include all movies, where the Sixth Sense contains the twist of all twists. (The ones below are from the Deathtrap movie -- the play, which I read eons ago, doesn't have as many).

1st Spoiler: Cliff isn't dead.
2nd Spoiler: Cliff and Sidney planned the whole thing to kill Myra.
3rd Spoiler: Cliff and Sidney are lovers (quite shocking back then).
4th Spoiler: Cliff is actually writing "Deathtrap."
5th Spoiler: Houdini's cuffs really exist, just as Sidney said, and Cliff accidentally uses them to imprison Sidney at the desk.
6th Spoiler (movie only): Helga TenDorp stumbles on the whole thing and takes the unfinished Deathtrap manuscript after Cliff and Sidney are dead, turning it into a hit.

---

I love the Gabriel twist in Next to Normal. If you're not familiar with the show or story, it really hits you deep when it's revealed.

---

Rupert Holmes' Accomplice was full of twists and misdirections culminating with the fact that you, the audience, ended up being the accomplice.

It is, imo, an underrated gem.

---

Curious Dad kills the dog and his mother is alive

The Gabe twist is great, and I've always been a fan of the twist at the end of Sweeney. (In fact, I think there's a clue that gives it away early in the original artwork. Sweeney has a bloody razor, but Lovett has bloody handprints clutching at her apron- like someone needed help and didn't get it.)

However, I'll always love the twist at the end of "A Little Night Music," when Fredrika pulls a zipper and accidentally discovers that Madame has been just a bag stuffed full of spiders the entire time.

No matter how many times I see The Mystery of Edwin Drood, I am always surprised by the true identity of Drood's killer. Also, the two lovers in the end. How unexpected. What a twist.

---

Cabaret anyone? The ending was so chilling and unexpected!

The end of A Chorus Line--the people Zach calls forward at the end are the ones who DIDN'T get chosen. I love the pause that tells you that they are as stunned by it as the audience is.