Odd things happen when someone drops an old couch onto the lush green lawn of the National Constitution Center.

"It's like Friends," one man cried, piling onto the cushions with his buddies.

Others traced an invisible curved line with their steps, staying far from the couch and its tenders, waving away offers of handout cards.

Some tourists on Independence Mall accepted an invitation to sit. Others shot cellphone photos. A few, touched by the effort, shared intimate details of their lives that they might have withheld if not for the public prodding of a worn, gray-and-blue sofa.

On Thursday, a sisterhood of the traveling couch continued to romp across Center City, the furniture lugged to prominent settings by Valley Youth House workers seeking to provoke conversations on a difficult topic: homelessness among lesbian, gay, bisexual, and transgender youths.

Cindi Canary, in town from Chicago, was willing to listen.

"As parents, we all see young adults in vulnerable positions - and often on our couches," said Canary, a political consultant.

She and Bob Kueppers, a retired accountant from Sarasota, Fla., sat back and held up hand-lettered cardboard signs, like those made by homeless people, that bore the social-media hashtag #CouchesDontCount.

That's the name of the Youth House campaign that aims to raise awareness and money.

In Philadelphia, about 40 percent of homeless youths are lesbian, gay, bisexual, or transgender, studies show. National statistics mirror that - and indicate more than 40 percent ran away or were forced out of their homes by families who could not accept their sexuality.

Many of them don't see themselves as homeless, because they usually sleep indoors - moving from couch to couch in the homes of friends, acquaintances, and strangers.

That drains their finances, and can threaten their health and safety.

Youth House workers are dramatizing those conditions with a donated piece of living-room furniture. On Sunday, the couch heads to OutFest at 12th and Locust Streets, and next week to a Wharton School student event.

At lunchtime Wednesday, the couch landed outside the Barnes & Noble store at 18th and Walnut Streets, steps from the gardens of Rittenhouse Square.

Women carrying pink Victoria's Secret bags glanced over and kept walking. People holding brown sacks from Hip City Veg stopped to chat. Babies rolled past in strollers.

"It's like, 'What's going on with this couch?' " said Kenny Polk-Jones, 25, a transgender person who a few years ago got help from Valley Youth House.

The Constitution Center offered both dramatic backdrop and curious setting.

Joggers ran by, slapping high-fives with Youth House workers. A couple of people stared from across the street, their backs to Independence Hall. A group of tourists walked out of the Constitution Center and past the couch, ignoring the white-shirted workers who beckoned them to sit.

"That's what happens to homeless people, too," said agency development officer Valerie Johnson, "so it's not anything we didn't expect."

Some seemed to think the couch was part of an art project. Or a protest.

Linda Giovinco, who was playing tour guide to friends and family from Kansas and Colorado, stepped away from her group - and pressed money into the hands of a Youth House worker.

"It makes me sad," she said. "There's a bunch of gay children whose parents don't accept them."

She knows. Her son, now 37, is gay.

"I loved him before he told me that," she said, "so nothing changed."

Fifteen-year-old Claudia Wolfer and her friends slumped onto the sofa, surrounded by a rainbow of red, yellow, pink, and blue pillows. They held up signs reading: "Where are you sleeping tonight?"

Studies show some youths become homeless when they age out of the foster-care system. Some end up living with predators, engaging in "survival sex" solely to keep out of the cold.

More than half of homeless gay youth endured sexual, physical, or emotional abuse in their family, studies show.

In the last five years, Valley Youth House has moved 111 gay or transgender young people aged 18 to 21 into apartments. That number, while small, represents lives newly stabilized, agency leaders said.

Now they hope extra funding can help them serve bigger numbers - if they can get people to listen and care.

"When I see young people, I stop to see what's going on," said Kueppers, the Florida accountant. He recalls having teenagers stay with his family, only later realizing they had trouble at home.

"Homelessness is not always visible," he said. "They're making a great point."