Michael Bergstrom is used to fielding strange requests. After all, “there’s not too many people running around with full suits of armor,” said the Renaissance re-enactor.

But this summer, the Seattle 35-year-old forge owner experienced a personal first. He received a call from a local real-estate agent asking if he would pose in full armor, in listing photos for a house that looks like a castle.

“The homeowners and I agreed that the future buyer of this house is most likely a lighthearted person that would appreciate the humor,” said broker Jonas Elber of his staging idea for the $600,000 Chattaroy, Wash., listing.

To take the gag further, the real-estate agent came up with clever ways of positioning Mr. Bergstrom around the house: In one photo, he is in the kitchen using a sword to chop oranges and cooking with ingredients labeled “powdered dragon scales” and “cream of gorgon soup.” In another, he is in a bathroom applying Armor All to his underarms.

As new agents flood a hot housing market—there are more real-estate agents than homes for sale in the U.S.—industry veterans such as Mr. Elber have had to get creative to convince sellers to list with them.

Michael Bergstrom in real-estate listing photos for a house in Washington.

Photo: Jonas and Associates

‘The homeowners and I agreed that the future buyer of this house is most likely a lighthearted person that would appreciate the humor,’ said broker Jonas Elber.

Photo: Jonas and Associates

Real-estate agents are also using these tactics to help sell houses that are a little odd and have trouble moving, even in such a strong market. Some feature the family dog (or their own) in photo shoots; one real-estate agent wrote descriptions of a home’s features in rhyming couplets.

“It’s not just marketing the listing and making the listing itself stand out from the crowd, it’s standing out as the agent that will do these things,” said Rachel Gannon, a real-estate agent in Dayton, Ohio.

Ms. Gannon dressed her 9-year-old in an inflatable alien costume for the February listing of a home in Kettering, Ohio.

As potential buyers scrolled through the photos on Realtor.com or Zillow, they were greeted by six standard images and then, abruptly, a seventh featuring the green alien seated, book in hand, on a living room settee. A few photos later, the alien is there again drinking coffee at the dining table, hiding behind the shower curtain in the guest bath and working at a bedroom desk.

“Earth to buyers!” the listing says, and includes references to an “out of this world” spiral staircase and an oversize garage with “room to dock your spacecraft.” It sold for $215,000.

Ms. Gannon said the theme was inspired by the neon green front door— the house sold in one day. Likely a result, she said, of the listing getting picked up by local news as well as Facebook’s “Nightmare on Zillow Street” and Instagram’s “Zillow Gone Wild,” which curate posts for their 137,000 and 1.3 million respective followers.

Real-estate agent Rachel Gannon's 9-year-old daughter brought attention to her listing photos dressed in an inflatable alien costume.

Photo: Aaron Lee

A visitor to the house for sale in Ohio.

Photo: Aaron Lee

The pages tend to focus more on houses with unusual characteristics: A mansion in West Olive, Mich., is featured, with a 1,000-square-foot room devoted to the homeowners’ collection of taxidermied mountain goats.

Ms. Gannon’s 9-year-old, the alien, was perhaps the most delighted by all the attention. “She was like, ‘Oh, my God I’m famous, I could end up on ‘Ellen,’ ” Ms. Gannon said.

Robert Gomez founded Jurassic Realty this past February. Taking a literal approach to his company name, the San Antonio, Texas, broker roped his wife and daughter into donning inflatable blue raptor and T-Rex costumes not only in the photographs for two listings, but also for the three-hour-long open houses.

“Some people just wanted to come by and take a picture,” Mr. Gomez said.

After only two days on the market, one of the listings had already received multiple offers, including one from someone who had only seen the listing online. “The main thing is to catch people’s attention,” he said.

Robert Gomez’s family member in an inflatable T-Rex costume in a listing photo for his Jurassic Realty agency.

Photo: Jurassic Realty

Charleston real-estate agent Elizabeth Baker often employs her clients’ dogs as one way of grabbing attention. Even if they don’t have dogs themselves, she’ll borrow the neighbors, or use her own. “It’s my little branding thing,” she said. “Any publicity is good publicity on a listing.”

For the castle house listing, the broker, Mr. Elber, decided to splurge by hiring Mr. Bergstrom, who had a legitimate, rather than costume, suit of armor, and he had to pay for Mr. Bergstrom to drive the five hours from his home in Seattle to the listing site. The 100-degree weather that day upped the ante of posing for outdoor shoots wearing over 100 pounds of metal.

“I can’t even open the visor by myself,” Mr. Bergstrom said of the suit’s unforgiving design. “So I really have to trust whoever is in charge of keeping me hydrated.”

While the medieval-inspired property was previously listed and sat, unsold, for over 300 days, this time, the homeowners have already received multiple offers. Mostly, they’re excited to have the house off their hands.

“We had no idea it would blow up like this, it’s been crazy,” said owner Shelly Bemis, 63, who works in the Spokane county treasurer’s office. “But the bottom line is to get it sold.”

Real-estate agents are looking for ways to stand out in a competitive field.

Photo: Jonas and Associates

Write to Rachel Wolfe at rachel.wolfe@wsj.com