"You tell me why," Lively said, prompting the explanation that supporters of Dallas' NBA team were offering a shoutout to fans of the NHL's Stars, who for years have yelled their team's nickname both times it comes up during "The Star-Spangled Banner."
"I definitely had a sneaking suspicion, but I didn't want to guess," the 20-year-old from Duke said. "So that's what I thought it was."
The Mavericks and Stars reached the Western Conference finals in their respective leagues together this spring for the first time in the 31 years since the NHL franchise moved south from Minnesota.
Lively and co-stars Luka Doncic and Kyrie Irving have the Mavs in the NBA Finals for the first time in 13 years, with Game 1 in Boston next week. The Stars will play at least six games against Edmonton for a spot in the Stanley Cup Final, which was last played in Dallas in 2000 when the clubs shared since-demolished Reunion Arena.
It's making for a busy spring for American Airlines Center workers who can convert the floor from ice to hardwood — or vice versa — in a matter of hours at the 23-year-old arena. They do that constantly for six months during the regular season, occasionally for a day-night doubleheader with less than five hours to spare between games.
By the time these NBA and NHL playoffs are over, the AAC, as the locals call it, will have hosted about 25 postseason games, after each team played 41 games there in regular seasons that started almost eight months ago.
It's just the sixth time that NBA and NHL teams sharing an arena have reached the conference finals together, and the first since the Nets and Devils in New Jersey in 2003.
"There's gonna be a lot of things sold in this stadium," Mavs coach Jason Kidd said, chuckling at himself while seeming to have the word "alcohol" running around in his brain. "A lot of water's going to be sold, so it's going to be an incredible time here in Dallas. It's going to be busy downtown."
The Texas Rangers won their first World Series last fall, an interesting twist considering they were a strike away from winning the title twice in 2011 when the Mavs were reigning NBA champs.
That 2011 championship is the only one for the Mavericks so far. The Stars won their lone Stanley Cup in 1999. Now the clubs are closer than ever to a Dallas double.
"It's awesome," Stars captain Jamie Benn said. "I think both franchises probably got some motivation from the Rangers as well. We're happy to watch the Mavs go on and do so well. And we're supporting them as much as they're supporting us."
Even a couple of out-of-town football stars are getting into it.
Kansas City Chiefs tight end Travis Kelce showed up in a suite with former Stars goalie Marty Turco and plenty of others for a 3-1 victory over Edmonton in Game 2.
That footage prompted fellow three-time Super Bowl winner and quarterback Patrick Mahomes, a Texas native, to post on X imploring his favorite receiver to "get out of my arena!!" Mahomes and his wife, Brittany, attend a fair share of Mavs games.
A night later, Mahomes and Kelce were sitting next to each other courtside when the Mavs beat Minnesosta 116-107 for a 3-0 series lead.
"It's just dope to see both of us in the same position right now," Mavs center Daniel Gafford said. "Something that you never think you would think on as a kid, but now that you're in a position of thinking about it, it's just like, 'Wow.'"
Nathaniel Lowe won his first Gold Glove at first base while helping the Rangers win the championship. The gregarious Lowe seems to relish showing up on the video boards when he attends Stars games.
"The DFW area has given me a lot — like, a lot," Lowe said, referring to the acronym that includes Fort Worth. "And I feel really fortunate to be part of a championship organization there. So if that can bleed into hockey and basketball and then, ideally, across the road to football too, then we've got a good thing going."
By "football," Lowe means the Dallas Cowboys, who play just a few hundred yards from the home of the Rangers in Arlington, halfway between Dallas and Fort Worth. One of the biggest brands in pro sports, the Cowboys haven't reached an NFC championship game since winning the last of the franchise's five Super Bowls to finish the 1995 season.
Dak Prescott is the latest quarterback to bear the burden of trying to get that playoff breakthrough, and he sees what's going on about 30 miles south of the headquarters of America's Team in a Dallas suburb.
"It's not jealousy, but yeah, it fires you up," said Prescott, who endured his biggest postseason disappointment in January with a shocking wild-card loss at home when the Cowboys were favored to beat the Green Bay Packers.
"I want it for them," Prescott said. "I want it because it only raises the stakes and makes it tougher on me. And I'm for that. Go win it. Rangers did it. Other two go do it. Put more (expletive) pressure on us."