John Legend, Kelly Clarkson and Carson Daly also get in on the fun in the new promo!
Stefani suggests a slumber party that Shelton initially blasts by asking, "What are we, in the fifth grade?" before Clarkson excitedly appears in her pajamas and the festivities really get going. What follows is an incredible night full of pillow fights, nail painting, music around the piano and some scared looks over Shelton's past mullet.
Host Carson Daly joins the gang next, starting to read them a bedtime story before they all nod off in their sleeping bags. "Sleep well, my angels," Daly says as he kisses Shelton on the head. "We've got a big season ahead."
In a previous promo, Stefani gushed over her return to the show following Adam Levine's departure after 16 seasons.
"I'm so happy to be back. My life changed so much on the show," she said in the clip. "And then to be with my best friend, Blakey, and to be here with Kelly and John, I feel pretty lucky to be here right now."
Shelton seemed pretty pleased with Stefani's return as well, gushing that he "always love[s] having Gwen on the show."
"I mean, this is the fourth season," he said, referencing Stefani's previous coaching stints in seasons seven, nine and 12. "She literally makes my day 100 percent better."
"It’s going to be fun and exciting," Stefani said. "Blake’s my best friend. So, I get to hang out with him at work. It’s going to be great."
As for the couple's relationship now that they're working together, a source previously told ET that they've never been better.
"Gwen seems secure and happy to be back. Their relationship is so different from when they first started dating on The Voice," the source said of Stefani and Shelton. "They're truly like a married couple who hasn't lost that spark."
The source added that for Stefani and Shelton, it "has been really sweet, because The Voice is where they fell in love, so being back on set seems to have stirred up some cute memories."
Season 17 of The Voice premieres Monday, Sept. 23 at 8/7c on NBC.
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Gwen Stefani Teases Her Return to 'The Voice' With Blake Shelton, Kelly Clarkson and John Legend