Fill in the blank: I was so frightened that I _____: A. Screamed, B. Fainted, C. Peed myself, D. Sang a show tune.

If you answered D, you are in luck. Two musicals with scary themes open Friday: “The Rocky Horror Show” at Park Square Theatre and “Night of the Living Dead! The Musical!,” a Minneapolis Musical Theatre production at Phoenix Theater. Later this month, Twin Cities Horror Festival features the Shrieking Harpies troupe in “An Improvised Musical Spooktacular,” which has the additional fear factor of being made up on the spot.

Despite having the word in its title, “Rocky Horror Show,” is apt to be less horror than camp, which also is true of the zombie-based “Living Dead.” But Shrieking Harpies shows, 60- to 75-minute musicals created by Lizzie Gardner, Taj Ruler, Hannah Wydeven and pianist Justin Nellis, do go for scares. Gardner thinks there’s a natural kinship linking horror, improv and music.

“There’s always that element of, ‘What’s going to happen? What is your scene partner going to do next?’ We scare ourselves sometimes,” Gardner said. “That can be a lovely rush, to have a partner make a choice that makes you go, ‘Omigod!’ ”

Gardner recalls one show — based, as always, on suggestions from the audience — in which she played a parent, shielding a child from harm. Suddenly, a hand snaked from behind her and freaked her out. But she had to stay on key.

“I was definitely not expecting it. You just have to go with it, and it’s one of those moments as a performer where you have to decide, ‘Am I gone now? Is my character being killed on stage?’ ” Gardner said. “That’s exciting: that feeling of not knowing what’s lurking around the corner.”

That sentence pretty much sums up horror’s appeal, whether on stage, in books or in movies. Flordelino Lagundino, artistic director of Park Square, thinks anticipation of the unexpected also is part of the allure of musicals, especially “Rocky Horror,” with its story of strait-laced couple Brad and Janet, who stumble upon a house where seemingly anything goes.

“I grew up in a very conservative household and, for me, ‘Rocky Horror’ means an openness I had never known before: about sexuality, about not caring what other people think. When Brad and Janet go to that house, they are insiders of society who become outsiders. They’re part of the mainstream world, and I feel like that house in ‘Rocky Horror’ is for — I don’t want to say misfits, but it’s for people who don’t feel like they fit in the mainstream,” Lagundino said. “Kids in musical theater often have felt like outsiders, and they find in theater a way to just be and not care what others think.”

Obviously, all three horror musicals are timed to take advantage of Halloween. Lagundino said Park Square wants to create a seasonal theatergoing habit, in the same way some groups celebrate Christmas by attending “A Christmas Carol.” Along with howliday spirit, nostalgia for the originals also is a selling point for the shows.

Ryan McGuire Grimes has become something of a specialist in horror musicals. In addition to directing “Living Dead” for Minneapolis Musical Theatre, he helmed MMT’s “The Toxic Avenger” and acted in its “Evil Dead the Musical.” He believes they transcend their movie origins.

“If you stage it in a way that the audience has to have seen the movie, then I don’t think you’re doing your job. It should be entertaining, regardless of if you’re a fan,” said McGuire Grimes, who thinks these shows grab audiences that aren’t typically attracted to musical theater (including his own in-laws). “But will people get more of the jokes if they’ve seen the movie? Of course.”

In the case of the two musicals based on horror classics, McGuire Grimes said, “Part of what makes them popular is people wanting to poke a little fun at parts where they’re cheesy or where the special effects are primitive.”

All three shows lampoon horror tropes, whether it’s a classic villain such as a vampire or dopey victims who know monsters are on the loose but still walk into a dark room without turning on the lights.

“Our mind-set is always around: What are specific things in the genre we can use?” Gardner said. “We’ll rehearse beforehand and brainstorm: What are things that come to mind in terms of tropes or characters? That’s also where I give Justin a lot of credit. If we do anything genre-based, he sets down an opening number based on that suggestion, puts everyone in the mood with music, and then he’ll continue to build on that.”

Although “Rocky Horror” and “Living Dead” have plenty in common with their O.G. movies, the stage shows are not duplicates. McGuire Grimes said that, for instance, “Living Dead! The Musical!” had to adjust the movie ending, since a black protagonist being shot by white police has a different impact today than it did in 1968. Lagundino was moved to put “Rocky Horror,” which inspired the 1975 cult movie, in his first season at Park Square because young staffers wanted to see what it’d be like today.

“What does it mean to do ‘Rocky Horror’ right now? For a new generation?” asked Lagundino, whose production emphasizes the gender fluidity that has always been integral to the show that asks us to do the “Time Warp” again.

Unlike the Shrieking Harpies, the directors of both “Rocky Horror” and “Living Dead” say their intention is not to frighten.

“We’re taking the framework of the movie, but we’re certainly not staging it to be a scary experience. It’s over-the-top fun, and that’s what I enjoy,” McGuire Grimes said. “Actually, I think it’s hard to scare people in theater, although I remember being freaked out by people in cat costumes when I was a kid and saw ‘Cats.’ ”

As horrifying as “Cats” admittedly is, it also demonstrates a point Gardner makes: that musicals, like horror, have a lot to do with helping theatergoers suspend disbelief and encouraging them to release tension, whether through a song or a scream.

Or maybe both.

“If it’s happening in the moment of the show that someone is dying, you can have that death on stage,” Gardner said. “But why not sing one last beautiful song before you go into the ether?”