The 49-year-old singer stopped by Late Night With Seth Meyers on Tuesday and joked about her unexpected relationship with the 43-year-old country star.
The conversation kicked off when Meyers reminded Stefani of a throwback pic she posted that featured her beau with his then-signature mullet. When Meyers went on to note that Stefani and Shelton likely had even more differences back in the '90s, she revealed that she "always think[s] about that."
"I never, never thought I'd get the opportunity to be with someone that has a mullet. Or had a mullet," she quipped of her fellow Voice coach. "Can you believe it? He actually had that haircut! He thought that was great."
Additionally, when Stefani appeared on Todayearlier this week, she joked about the photo, telling Hoda Kotb and Andy Cohen that "life is full of surprises."
Despite their loving relationship, Stefani already proved that she plans to win this season of The Voice by blocking her beau from a contestant during the premiere episode.
"This season, I'm going to win. Generally I'm not a competitive person, but when it comes to this show I feel like it really does bring it out of me," she told Meyers. "... My team this season is ridiculous. They're not only just super talented, but [also] I love them. They're very lovable. So I'm having a lot of fun."
"I really do want to win," she added. "I really want to win."
Back in August, a source told ET that Stefani and Shelton were thrilled to once again share the Voice stage.
"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. "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."
Watch the video below for more on the happy couple.