Gwen Stefani on What Blake Shelton Thought of Her Cowgirl Costume at Las Vegas Residency Debut (Exclusive)

The 48-year-old singer playfully told the crowd it was her 'fantasy' to wear the ensemble -- but was it his?

Gwen Stefani's Just a Girl Las Vegas residency debut was full of showstopping costume changes -- but only one outfit was a "fantasy" for her to put on. 

The 48-year-old singer playfully told the crowd at Planet Hollywood Resort & Casino's Zappos Theatre on Wednesday night that it was her "fantasy come true" to wear a cowgirl ensemble in front of her country singer beau, Blake Shelton. But what was his reaction to seeing the dazzling Jeremy Scott for Moschino look on stage? Apparently he's seen it before. 

"You know, he's like my bestie, so of course he's seen everything as it's been going," Stefani revealed during an interview with ET's Keltie Knight in Las Vegas on Thursday. "[I'm] just bouncing [ideas] off of him and stuff like that." 

"But I don't think he knew what that whole ending scene was going to look like," she admitted. "I could picture it in my mind, but to make it finally look like that, it was beautiful... I was trying to ask him [what he thought]. He had to come and leave. He's doing the blind [auditions at The Voice] today."

Shelton's trip to Las Vegas may have been short, but he was completely there for her during the show, as fans even spotted him with Stefani's youngest son, 4-year-old Apollo, on his lap ahead of the concert. For Stefani, sweet moments like that are the ones she cherishes -- and tried to wrap into her show. 

"The ending of the show, what I was trying to say in a huge kind of love note way is just how amazing life can be, where everybody has to go through these challenges and these dark times, and then there's always a rainbow," she explained. "We literally put a rainbow on the screen, and sunflowers. And that's what my life feels like right now in so many ways."

"I'm so grateful to get to this point," she continued. "There's always going to be more stuff that's going to happen and I know that. But I have that seed of faith that my parents gave me. I just always try to trust that I'll find the answer."

See more on Stefani in the video below.