Jonathan and Drew Scott were blown away by 'hard-working' Jay Leno, who pitched in on 'Celebrity IOU' while recovering from garage fire, motorcycle accident: 'No pain killers, no complaints'

For all the talk about the glam lives that celebrities lead, twin brothers and HGTV hosts Drew and Jonathan Scott have a very different perspective.

They've seen Heidi Klum, Jay Leno, Glenn Close, siblings Derek and Julianne Hough and more get down and dirty during home renovations. All of those celebs, plus Kristin Chenoweth, Emma Roberts, Taraji P. Henson and Kristin Davis, are part of the new season of their Celebrity IOU, in which the remodel experts help stars transform a space for a loved one.

"I love that Heidi and all the different celebrities, they want to get hands on," Drew tells Yahoo Entertainment. "They don't want to just say, 'Go do this for me to give back to somebody.' They want to physically get hands-on."

Notably, Leno did it at what turned out to be quite an inconvenient time for him, following severe injuries in November and January.

"He had a couple of issues that had happened," Jonathan explains. "He had burned his face in an accident, and then he had a motorcycle accident and he broke his collarbone, his ribs and he busted his knee. He was in with us that same week that he had the accident, with all these broken parts, and he didn't want to slow down because the family he was giving back to, they were about to have a baby in a matter of weeks, and he wanted to get this done. No pain killers, no complaints."

Drew adds, "I cannot wrap my brain around how down to earth and just hard-working Jay Leno is. He is just like a salt-of the-earth kinda guy. He's incredible."

In the season premiere, it's Klum who impresses during the overhaul of the residence of Lucia, her housekeeper of 17 years. The model's present throughout, even hammering and stepping onto the property's roof.

"Heidi is a force," Drew says. "What I don't think people really realize is, she doesn't have a whole team of people around… She wants to do it herself. She wants to do it right. So every project we gave her as well, she would find out the proper way to do it, go back to it… talk about German efficiency. She wanted to make sure that she was perfect. And she knocked it out of the park."

Jonathan agrees.

"She always has this fun energy on any of her shows, everything she does. But picture her wielding a sledge hammer with that energy," he says. "It was almost like a child, when you see a kid that has that wonder and that dreamy look to them, that was her all the time, and she's up on the roof of the house fixing some patching on the roof. She was smashing up this old kitchen."

Somewhat surprisingly, eight-time Oscar nominee Close also was quick to roll up her sleeves.

"One second, let me just pull out my bucket list," Drew says. "Check, check! Didn't even know that was on my bucket list. Who would think that you're gonna get to work with an icon like Glenn Close? And not just that, I didn't know a lot about her personal life. You know, she lives on a ranch... does a lot of tending to the property and animals herself. She gets on site, and she's like, 'Outta my way.' Jumps on the excavator, smashes this shed down and she's laughing. It was so funny… I think we're gonna break the internet with this footage."

Jonathan swears that Close was so happy, she might make a career change.

"Our apologies to Hollywood if she gives up on being the best actress in the world because she wants to start doing what we do," he says. "She loved demolition. It can be addictive when you start to smash things. She was filming in Paris, and she was flying back to be a part of this, over in Maine, on the East Coast. She's giving back to the woman who runs her charity, and so I thought that was pretty amazing, too. To see that kind of a commitment."

The Property Brothers stars, who have renovated more than 630 homes on their various shows, probably had the most fun all season when they worked with another set of siblings: Derek and Julianne Hough.

"They were joking about how everyone thinks they're twins but they're not," Drew says. "But you would think they're twins, because they finish each other's sentences. They both, they don't just talk. They express every word with their body… The way they are together, and the way we are together, you kinda see that sibling dynamic… it was so much fun. I don't think I've laughed that much during demolition and construction in so long, but it was fun. And there were so many dance competitions."

Anybody who's seen Celebrity IOU knows that it's about much more than the drywall, no matter who's overseeing the construction. The show is really about relationships and showing gratitude.

Jonathan notes that it gives the audience a chance to see "the human side" of people like Leno.

"For me, that's the most interesting part," he says. "Getting to see the celebrities in a different light, in a different setting. You really see, I think, their true self, as opposed to, you know, normally you're doing interviews and you're on a red carpet and you're just kinda seeing that being on. I like it seeing people when they're not on."

The season premiere of Celebrity IOU airs Monday, May 15 at 8 p.m. on HGTV.