Meet the man behind the most amazing treehouses you’ve ever seen.

Pete Nelson has built impressive forest homes, playhouses, recording studios and more on his Animal Planet show Treehouse Masters and counts Zac Brown and CeeLo Green among his clients. The “tree whisperer” recently stopped by PEOPLE to talk crazy requests, celebs’ construction skills, and his dream client.

For Zac Brown’s summer camp in Georgia Nelson surprised the Grammy winner with a “Space Crab” structure. “He lit up,” Nelson tells PEOPLE in the video above. The structure made of metal and glass, instead of the usual wood, Nelson says, will last 100 years.

CeeLo Green’s backyard recording studio in the trees took Nelson out of his comfort zone too. When the former The Voice coach lost his voice during the episode due to laryngitis, Nelson stepped in to test drive the music space. “I found myself singing,” he says. “Bad idea, but it was caught on tape, season two.”

One celebrity client has so far eluded the builder and TV personality: Grace Vanderwaal, winner of America’s Got Talent told PEOPLE that she would use some of her $1 million in prize money from the show to have Nelson build her a custom treehouse. The project, however, is still in the works because the young singer lacks the necessary trees in her yard. The pair are currently looking for an alternate location. “We’re crossing our fingers that we can create a treehouse for Grace,” Nelson says.

Treehouse Masters returns to Animal Planet for its 9th season this summer.