Millennials and Gen Z are excitedly buying Lego, plushies, and other toys. It's becoming big business.

As a child, you may have sung along to Toys R Us' iconic jingle about not wanting to grow up. Decades later, many millennial and Gen Z adults are taking that motto seriously.

Adults are rediscovering how Lego, stuffed animals, and other toys brought them joy. Now that they're earning their own money, they can afford the things they once played with or circled in catalogs. Hobby spending — which includes hobby shops, arts and crafts stores, and outdoor recreation providers — rose 7.9% year over year in August, according to an analysis by the Bank of America Institute.

Devin Byron, 25, had a collection of American Girl dolls growing up, but her interest in playing with them fizzled out around middle school. However, her love for them never really went away. And now, working an office job, she can buy her own.

In February, she and her friend went to the American Girl store in New York. Byron purchased the historical doll representing the '60s, Melody, which cost $135 with the book, plus $34 for accessories.

"I feel like a lot of collectors now are, I would say, healing their inner child because some people couldn't get maybe American Girl dolls growing up, but now they can," Byron said. "And it's an adrenaline rush too."

She's not the only adult contributing to the toy economy. Market research company Circana found that adult-only households made up over half of toy sales in the first half of this year, and that overall toy sales for adults increased 25%. Some adults may buy toys to bring nostalgia back into their lives or to avoid doomscrolling. For others, it's to make a profit.

"We're seeing toys increasingly function as hobbies, fandom ecosystems, and social experiences rather than traditional children's products," said Kristen McLean, vice president of client insights for Circana's Entertainment Knowledge Group. "That's expanding the consumer base and creating new opportunities for manufacturers and retailers that understand how to engage collectors, enthusiasts, gifters, and self-purchasers."

The rise of 'kidulting'

Jay Berino, store manager at the Lowry Town Center Timbuk Toys in Denver, pointed to "kidulting," the trend in which adults engage with childlike toys and hobbies, as coming from adults seeking distractions and nostalgia — from buying Pokémon cards to lava lamps.

"As much as we're a toy store and people hear toy store and think of kids, we sell to a lot to full-blown adults, and that drives a huge chunk of our business," he said.

Syls Farmer, 32, runs a vintage online store specializing in toys marketed to girls. Her store, Mema's Doll Shop, was inspired by her grandmother, who ran a couple of toy stores back in the day. Farmer said adults buy from her for themselves or for their kids so they can experience their past.

"A lot of people are dealing with a lot of pressure in this general economy and the world in general," Farmer said. "And I think that these items of childhood are bringing back feelings of comfort and peace that I think a lot of us need right now."

Farmer also buys toys for herself, including her first American Girl doll through Facebook Marketplace — Nicki, one of the '90s-inspired dolls.

Even crafters are getting in on the toy craze: Abby Glassenberg, the president of the Craft Industry Alliance, said that homemade Labubu-esque bag charms have taken off, with crafters making their own customizable charms from crochet or felt.

"People are definitely still spending. I think craft in some ways is resistant to market up and down," Glassenberg said. When the market is up, people pour more money into their hobbies, whether that's getting premium materials or even traveling to somewhere catered to their favorite crafts.

"When the market is down, and people's budgets are tighter, they want to make something for a gift rather than buy it," Glassenberg said.

Collecting toys

Emma Wynn, 28, has 120 Jellycat items, a popular stuffed-toy brand that includes animals, food, and more. Wynn's collection began when she bought a scuba diver egg while browsing at a garden center with her family, sparking a feeling of childlike happiness.

Prices range on the Jellycat site; for instance, a heart dragon is priced at $80, a carrot cake is priced at $45, and bear winter decorations are priced at $28. Wynn funds her collection with money she earns from content creation, rather than from her corporate job.

Wynn thinks adults buy toys because they bring back happy childhood memories, can provide a dopamine hit when someone finds something they've been searching for a while, and can connect them with others who are building similar collections.

"It feels very empowering to be unapologetic about the things that bring us joy and happiness, whereas before maybe I would've been embarrassed about it," she said.

It can also be a tangible way to remember a memory. For instance, Wynn's soon-to-be mother-in-law bought her a Jellycat flower bouquet to celebrate her new engagement.

Fueling an income

Harrison Woodward, 28, said building and playing with Lego sets was a large part of his childhood. For one birthday in his early 20s, his aunt bought him a Lego Porsche car model, reigniting his passion for Lego sets. He put on a streaming show after a long day of work and started to build the over 1,000-piece product.

"It was just the most therapeutic, peaceful activity," he said. "You could sit there for a few hours, a few days in a row, and complete a set and see it come together and marvel at all the different engineering things that they put into these sets now."

He left his job in insurance to focus on content creation full time. He posts about his Lego collection and passion for cars; he recently started collecting Hot Wheels, another childhood favorite. He has spent thousands on Lego and is running out of space in a room that's filled with his collections. He still tries to find a balance so that building isn't just for content, such as taking his time to build a CaDA car set in the evening.

Woodward thinks adults might be purchasing toys to invest some time in their hobbies and take care of their mental health.

"I think the stigma has kind of lifted over collecting and everything," he said. "I think that for a long time people thought any of this stuff was strictly for kids, but as the years have gone on and adults have continued to adopt it, the stigma continues to go further and further away."

Trading cards have also become a major area of interest for some adults. Kian Golshan previously told Business Insider that Pokémon is a lucrative side hustle. For instance, he sold a Japanese-edition Charmander for $750 that he bought for $59.26. As Business Insider's Samuel O'Brient previously reported, Golshan was able to put the analytical skills that he developed while working in finance to work.

"It helps me kind of think through the risks and when to take profits, when to sell, what to hold, what's my like risk profile, what's tracking the market," Golshan said.

Byron, the Gen Zer who bought an American doll, still has her collection of dolls from her childhood. Plus, she has her most recent addition displayed in her room.

"I'm actually thinking about going back to the store again," she said. "Maybe I'll walk out with another doll. I guess we'll see."