Blake Shelton calls his fan club the BSers. He drinks out of a mug emblazoned with the initials “BS.” And on Friday night at Xcel Energy Center, he sure spread the BS — in a good way.

He is a country star who lives by his wits as much as his songs. That’s why he’s become such a successful presence on NBC’s “The Voice” as a coach. That’s why his opening concert in a two-night stand was so triumphant. The BS worked.

Throughout his two-hour performance, Shelton, 40, mentioned that this was a special night. He talked about being nervous. So he had to keep sipping some presumably alcoholic beverage from his BS mug.

What was special — well, extra special actually — was an appearance by his love interest, pop star Gwen Stefani, on their duet “Go Ahead and Break My Heart.” He’d joined her last month at the X on her concert tour for the same song. She just happened to be in Minneapolis on Thursday to perform for 14,000 at the annual Target managers meeting.

Thanks to Target, more than 10,000 Shelton fans got treated to the duet in St. Paul. Shelton started singing, and Stefani waltzed out after the first verse without introduction. The tall dude in the blue jeans and sleeves-rolled-up blue shirt was all smiles as he sang face to face with Stefani, dressed in a silver lamé jacket, matching shorts and over-the-knee black boots. The crowd went wild, and the happy couple hugged at song’s end.

Stefani stuck around for one song of her own, 2005’s “Hollaback Girl,” her biggest hit that proved hip-hop pop can score with a country crowd. Afterward, Shelton returned to the stage and bowed to her several times.

Although Stefani’s appearance wasn’t a complete surprise (put 2 + 2 together with the Target meeting), her performance with Shelton was more exciting than when Miranda Lambert, his then-wife, joined him in 2012 at the Minnesota State Fair. On that night, Lambert didn’t get her own solo number.

Shelton needed the BS to carry the rest of the night Friday because his repertoire is long on ballads and medium-tempo songs, and that combination can make a show drag in a hockey arena.

He covered Rhett Akins’ “Kiss My Country Ass” to give the early part of the set a kick in the butt. Shelton’s major up-tempo hit “Hillbilly Bone,” which evokes Big & Rich, perked up the middle of the show.

And in the home stretch, after Stefani’s star turn, Shelton rocked out with the breezy, romantic “Honey Bee,” the bro-countryish “Boys Round Here” (featuring opening act RaeLynn, an alum of Team Blake on “The Voice”) and an energetic if overamped encore of Kenny Loggins’ 1984 rock hit “Footloose.”

For much of the show, Shelton had been tongue-loose. Between the ballads (“She Wouldn’t Be Gone” was a heartfelt, deep-voiced highlight), he babbled about whether he was in Minneapolis or St. Paul, how good or “sucky” his own songs were, how good or pitchy the crowd was during several singalongs and how those big ole boys in the front row got dragged to the concert by their wives or girlfriends.

In the end, all the BS was only part of the story. Because BS + GS = Big Success.