It's no surprise to see Marjorie Congdon on stage in "Glensheen"; she's the star of the show that runs through July 24 at the History Theatre. But lately, she has been popping up in the audience, too.

As the musical returns to History Theatre for the sixth run since its 2015 world premiere, expect some audience members to be dolled up in the signature sunglasses and scarf worn by Congdon, who's played by Jen Maren. That has become more common each time the show returned. In a Duluth stop on the tour that preceded the St. Paul run, four faux Congdons sat in a row, all in pretty much the same thing Maren wore on stage.

History Theatre artistic director Ron Peluso has mixed feelings about costumed audiences.

"I discourage the promotion of that because, ultimately, the play is about the murder of two women. We don't want to make a mockery of that," said Peluso of the musical, a funny-but-respectful retelling of the tragic 1977 murders of heiress Elisabeth Congdon and nurse Velma Pietila — murders in which Congdon's daughter Marjorie was a suspect.

He thinks writers Jeffrey Hatcher and Chan Poling's depiction of Marjorie inspires fans to ape her.

"It's a combination of the boldness, the drama, the gutsy portrayal of this character. It's both the character and the larger-than-life portrayal. And I think it's Jen Maren, too. Sort of a Jen Maren fan club," said Peluso. "I want people to see the show because it's such a fascinating part of Minnesota history but this is not 'The Wizard of Oz,' where someone might show up dressed like the Wicked Witch or something."

Funny he should mention "The Wizard of Oz," because an Aug. 10 screening of the classic Judy Garland film at the Heights Theater is bound to attract a bunch of Dorothys, clad in blue gingham jumpers.

"We've had anywhere from a 40-year-old Dorothy to a 5-year-old," said Heights owner Tom Letness, who scheduled an additional "Oz" after one in June sold out.

Not all movies inspire costumes — Letness hasn't seen a ton of blue suede shoes at the current "Elvis" — but there have been dolled-up folks at the "Downton Abbey" movies and at many classics. Memorably, that includes "2001: A Space Odyssey," where attendees included a man dressed as that film's famous monolith.

"This was maybe five, six years ago. He had this big, flat, black cardboard box on his body and his head and legs stuck out of it," Letness recalled. "It was obviously removable because he took it off to watch the movie."

Letness thinks costumes happen because of affection for a film and a desire to briefly join its world.

"They identify either with a particular character or message and it inspires them enough to dress up," said Letness, who digs the fancy duds (although reports from around the country last week indicated fans at "Minions: The Rise of Gru" caused some disruptions). "I always think it's super-cool because it means they really, really love the movie."

A fan favorite that has brought out corsets and waistcoats at the Heights is "Moulin Rouge." It may be that flashy costumes are more likely to inspire patrons — "Moulin Rouge's" memorable couture earned designers Catherine Martin and Angus Strathie an Oscar.

The flashy rule seems to be true at the Orpheum Theatre, too. A recent run of the stage version of "Moulin Rouge," whose costumes won Catherine Zuber a Tony Award, also attracted audience members in racy, can-can finery.

"We had people in burlesque-inspired clothing, which definitely matched the theme of the show," said Dale Stark, public relations manager for Hennepin Theatre Trust.

Kids are most likely to don costumes, possibly left over from Halloween, to go to the theater, which is why Stark said ushers always know they'll see plenty of princesses at "Cinderella," "Frozen" and their ilk. "The Lion King" brings out little lions and even some big ones.

Iconic looks make it easy to dress up for a musical such as "The Book of Mormon," Stark said.

"Shows that have almost a cult-like following, their fans really get into dressing up. So we see lots of people at 'Book of Mormon' in the white shirt and black tie," said Stark, who also says "Rock of Ages" brings out its share of mullet wigs (hopefully, they're wigs) and '80s jeans. Even a show such as this month's sold-out Weird Al appearance will have fans imitating his parody videos, which means Weird-Al-as-Madonna and Weird-Al-as-Coolio could be a thing at the State Theatre show July 24.

"They want to feel like they're part of that show's community," said Stark. "For us, we feel like it helps spread the energy to everyone else who's attending. Like there's a buy-in: 'Omigosh, this is going to be a fun show.'"

That's why Stark thinks costumed patrons are great for everyone — well, unless you happen to end up right behind someone in a "Lion King" giraffe headdress. In a way, those enthusiastic theatergoers are getting the show started early, extending the experience all the way out to the marquee.