When Lazarus House executive director Danielle Sampey first got pitched a reality show, she was none too keen on the idea.

"One day I got a phone call from a producer who said he wanted to put together a documentary on volunteerism," Sampey tells CultureMap of the unexpected spotlight on her small charity, one "with a small staff and a smaller budget."

"I was apprehensive to have him film our clients, because our clients have health conditions," Sampey says.

Lazarus House, located in Houston's Third Ward, is an exercise facility dedicated to helping people suffering from disease-related muscle loss. But eventually — and now thankfully — Sampey relented.

It was the word "reality" in the contract that really stopped her in her tracks, Sampey says. "That freaked me out, because you know reality TV. I just wanted to make sure — nothing against Ozzy Osbourne — but make sure that's not who was going to volunteer, getting bleeped every other word," she says.

At the time the producers made their pitch, Sampey and her staff had no familiarity with the ABC show, Secret Millionaire, and weren't sure what to expect. But it wasn't Ozzy Osbourne who appeared on her stoop, it was two normal-seeming folks by the names of Gary and Diane Heavin.

"They were beyond nice, very genuine people," Sampey says of the husband and wife duo, who helped out with minor repairs and were trained in Lazarus House's exercise regimen to work out with a few of the non-profit's clients. "We were training [Diane]," Sampey says, "and lo and behold, they own Curves! The volunteer director was like, 'Oh my God, I was telling Diane how to do lunges.'"

The Heavins spent a full day exercising with clients and helping out around the converted four-plex, and Sampey says that despite their secret identities, she just had a feeling they were good people.

The Lazarus House staff is still reeling over the big reveal.

"I'm still shocked, still dumbfounded," Sampey says. "We knew something was up when they came back, but we had no idea it would come to such an amazing ending."

The Heavins provided Lazarus House with enough funding to sustain their programming and put away a significant nest egg toward the eventual purchase of Safe Haven, the converted house the charity operates out of.

Sampey says ABC came across their small operation because one of the producers, whose mother had Mutiple Sclerosis, was researching charities. He told Sampey off-camera that he wished he had had access to an organization like Lazarus House for his mom.

"It's embarrassing for me, but when he told me that I just burst into tears. I went over and asked him [how he found us] after Gary and Diane gave us the check, and there's no doubt to me there's a God."

In the episode, which airs on Channel 13 at 7 p.m. Sunday, the Heavins also are benefactors of the Sean Ashley House in southwest Houston, which helps people with disabilities, with a focus on autism, and No More Victims, a non-profit in east Houston created for children whose parents are in prison. It was founded by former probation officer Marilyn Gambrell.

Join Lazarus House for a viewing party of their Secret Millionaire episode Sunday at 6:30 p.m. at the Chocolate Bar in Rice Village.

See a Channel 13 story on all three Houston non-profits featured in Secret Millionaire: