The Mickey Mouse-shaped topiaries in front of Kelsey Hermanson’s house are the first hint at what visitors will find inside.

“You know how when you’re walking through a Disney park, and you have the option to go to Tomorrowland or to Fantasyland, and you have these different worlds that you get to sort of walk through and be in?” said Ms. Hermanson, 37. “That’s kind of how our house is.”

That is to say, each room in Ms. Hermanson’s 3,300-square-foot Seattle home has its own Disney-inspired theme.

The stairwell, for instance, pays tribute to “Peter Pan” with star-shaped pendant lighting fixtures, vintage décor on the windowsill that recalls Captain Hook’s galleon and wall decals of Wendy, her siblings and Peter scaling the wall.

Ms. Hermanson’s living room, anchored by an ocean blue sofa and a shadow box coffee table, calls to to “Lilo & Stitch” with character figurines, coastal accents and a thrift store oil painting adorned with stickers of the characters.

The dining room, fittingly, hearkens to “Beauty and the Beast” and Lumière’s warm hospitality — and so on and so forth. “Our house is not subtle by any stretch of the word,” said Ms. Hermanson, a stay-at-home mom and content creator, of the home she shares with her husband, Eric, and two children. “But I think the styling is a little bit more elegant.” That is to say, the Disney characters aren’t always so obvious in her rooms and she doesn’t plaster her home in merchandise.

The desire to take home a piece of the Walt Disney Company, which marks its 100th anniversary on Oct. 16, goes back to the company’s earliest days. Walt Disney himself began selling Disney merchandise in the late 1920s and Disney memorabilia, like an original Space Mountain vehicle which sold at auction for $40,000, can garner high bids.

Now fans are looking beyond collectors’ items to fill their homes with Disney, which the corporation itself has embraced through partnerships with Ruggable and the wallpaper manufacturer Sanderson. For some grown-up Disney evangelists (also known as “Disney adults”), it’s not enough to pepper in a few Donald and Mickey tchotchkes — they want the whole house swathed in Disney décor.

Part of Disney décor’s prevalence is its success on social media. On TikTok, for example, the hashtag “Disney home décor” has more than 42 million views and “Disney home” has over 275 million. Ms. Hermanson grew her Instagram following of more than 150,000 by sharing photos and videos of her rooms and her D.I.Y. projects.

Though Ms. Hermanson does earn some income from occasional sponsored posts (not for Disney) and affiliate links, she maintains that her designs are for her enjoyment first. “If social media went away tomorrow, I’d still be happy and be like, ‘Well, I’m so glad I was able to bring my little idea to so many people,’” Ms. Hermanson said. “I’ll probably be 80 years old and still decorating.”

Disney first captured Ms. Hermanson’s attention during her childhood when she watched, and loved, the ’90s animated films. That affinity for Disney strengthened as she and her future husband bonded over Disney vacations as they dated. “We really like the history of Disney, and just the way the Imagineers are able to create this other world that you can go experience,” Ms. Hermanson said, referring to Disney’s research and development arm. “It’s a departure from reality.”

Disney-Meets-Dopamine

Incorporating Disney at home is not one-size-fits-all. Ginny Phillips, a blogger in Nashville, takes cues from Disney’s parks with a dopamine décor twist. “It’s just that super happy, bright, rainbow explosion,” said Ms. Phillips, 39. “I really think that it does boost my mood.” She shares her house with her husband and three children (all of whom, she said, are happily onboard with the Disney-inspired décor).

Though her daughters’ bedrooms were long decorated in Disney themes (her six-year-old daughter had a nursery inspired by the ride It’s a Small World), the parks were Ms. Phillips’s pandemic-era muses. “We couldn’t go to the parks because they were closed,” she said, and the extra downtime allowed her to focus on other rooms in her home.

In an upstairs hallway, Ms. Phillips, who has done occasional promotional posts in exchange for Disney goods or tickets, painted a pattern reminiscent of Spaceship Earth, Epcot’s geodesic dome. “I posted a step-by-step tutorial, and people are still, almost four years later, recreating that,” she said. A gallery wall of Disney artwork sits opposite the hallway.

In her office, Ms. Phillips painted a rainbow version of the Spaceship Earth design, and incorporated retro accents like a burnt orange sofa set against a backdrop of rainbow-hued wooden planks and a monorail print. “The parks are just so, so important to me, and there’s so much nostalgia there because I visited as a kid,” Ms. Phillips said. “But then also my kids have grown up there.”

Be Our Guest!

For those not part of the Disney fandom, such allegiances to the conglomerate may puzzle. While people arrive at their Disney design choices for different reasons, nostalgia, it seems, is often the impetus.

“Many of us have fond memories of watching Disney movies with our families, especially millennials who grew up in the Disney renaissance,” said Adriane Brown, an associate professor of gender, sexuality and women’s studies at Augsburg University in Minneapolis. The “Disney renaissance” refers to the decade between 1989 to 1999 in which Disney’s animated films took on more Broadway-like qualities and sharper animation, with films like “Aladdin,” “The Little Mermaid” and “Tarzan.” Notably, the era produced “Beauty and the Beast” which, in 1991, became the first animated film to receive a Best Picture nomination by the Academy Awards.

Millennials grew up in an era when Disney experienced growth beyond the films: The brand expanded into the cruise industry, purchased Broadway’s New Amsterdam Theatre, and saw the Disney Channel become a central part of youth culture.

“I think the nostalgia millennials in particular have for Disney comes from growing up in a Disney-saturated media culture,” Professor Brown said. The television element was particularly instrumental in introducing children at home to Disney characters. “After Disney bought ABC in 1995, characters on ABC sitcoms — particularly the TGIF comedy block, which was popular with families — started visiting Disneyland and Disney World,” she said. “For many ’90s kids, this was their first real look inside the parks.”

The Mouse in Their House

Where there’s budget-friendly D.I.Y. décor, there’s also high-end, bespoke design. In Golden Oak, a development in the Walt Disney World Resort in Lake Buena Vista, Fla., home prices start in the low millions (a 6,756-square-foot house currently on the market in the community is available for just shy of $12,000,000) and that’s not counting the décor.

Toni Sims, an interior designer in Orlando, worked on the Magic Kingdom’s design team before opening Toni Sims Design Studio and now has clients all over the country. For her clients in Golden Oak, she designs immersive Disney-themed rooms. “It’s like this challenge of, how can we give park-level-quality experience for our clients in their homes,” she said.

One recent project of hers was an “Aladdin”-themed guest bedroom. “We customized every piece that you see,” Ms. Sims said. This includes the magic carpet canopies over the beds and a divider, which separates a reading nook from the room, studded with acrylic and resin gemstones. “At night it is just absolutely stunning because they just reflect so much of the light when you turn the lights on in the room,” Ms. Sims added.

At a different house in Golden Oak, a room creates an underwater illusion with hand-painted water ripples on the ceiling and a starfish-embellished chandelier. The bottom of Ariel and Prince Eric’s boat juts out from the ceiling, too. There’s no mermaid in sight, but the aqua-hued room with an oversized clamshell headboard unquestionably pays tribute to “The Little Mermaid.”

Disney isn’t just for the kids: Child-free adults incorporate the Mouse into their house, too. In Columbia, S.C., Laura Chatterton and her husband, Chris Chatterton, both 36, have Disney merchandise throughout their home and pay homage to hidden Mickeys found throughout the parks. Ms. Chatterton, who grew up in Michigan, watched the Disney movies as a kid and traveled to the parks with her family. She and her husband discovered that they enjoyed trips to the parks together and they still go once or twice a year.

“Disney’s just our thing. It’s what we love doing. I think everyone has their own passion or hobby they like, and Disney just happens to be ours,” Ms. Chatterton said. Now their house has an extensive mug collection, Disney utensils, and several prints throughout.

In 2018, they combined their love of Disney with their love for plants when they began selling 3-D printed planters. Popular forms in their lineup include Cinderella’s castle and Spaceship Earth. “We were just blown away by the demand for it,” Ms. Chatterton said. They now both work full-time for their company, Galactic Garden Arts.

For some, however, Disney décor is symbolic. Uriel Diaz, 35, grew up as one of four siblings with Mexican immigrant parents. “Their idea of the American dream and the best that they could give their kid was Disney,” Mr. Diaz said. “My crib was Mickey Mouse and Minnie Mouse. The whole nursery was Mickey and Minnie.” While his parents couldn’t afford to take them to the parks, they ensured that the children had access to the movies and clothing.

Today, Mr. Diaz works at his parents’ antique store, which goes hand-in-hand with his ever-growing Disney collection. He incorporates his collectibles in surprising ways throughout their San Antonio home, like turning a Disney VHS collection into a gallery wall.

Mr. Diaz’s décor is nostalgic, but it also, to him, serves as a reminder of what’s possible. “That’s another thing about being a ‘Disney adult.’ A lot of us didn’t get to have all of these things because of finances or lots of siblings or whatever,” said Mr. Diaz. “So it’s kind of just healing that inner child by giving them that, giving them all the things that they wanted when they were little and reminding them: You are worth having it.”