No, not his Mean Joe Greene jersey or a terrible towel. Rather, it's his fiancée, Audra Marie, whom the True Blood actor first met – and fell in love with – at the 2009 Super Bowl, the last time the Steelers won.
"She was actually down there with some of her girlfriends for some of the festivities, and we met on our way into the Commissioner's Ball that year," Manganiello, 34, told PEOPLE at Saturday's Producers Guild of America Awards in Beverly Hills. "Football was kind of how we met."
And they bonded over his beloved team's victory. "She was my good-luck charm, and has been ever since," Manganiello says with a laugh. "She waved my Terrible Towel, and the Steelers came back and won the game."
Like any good lycanthrope, Manganiello will surely be wide-eyed and frothing at the mouth come Feb. 6, when Pittsburgh meets Green Bay in Super Bowl XLV. He can't help it, he explains – it's in the blood.
"I come from a long line of very superstitious Steelers fans," Manganiello says. "It can get a little weird. My dad is a very superstitious Steelers fan, and we all have to stay in certain positions because [he'll] make sure that you cannot move if the Steelers are winning. We care a lot, but it's a little OCD" – obsessive-compulsive disorder.