Alex O'Loughlin's Steve McGarrett and Jay Hernandez's Thomas Magnum will say aloha to each other when the two Hawaii-set CBS dramas from Peter M. Lenkov cross over in back-to-back episodes on Jan. 3. In fact, Lenkov says half of the crossover has already finished filming. “In a way, Higgins and Magnum become witnesses that Five-0 needs to help them,” says Lenkov of the crossover. “And our two worlds collide!” Lenkov, who had been trying to pull off the Hawaii Five-0/Magnum P.I. crossover since last season, adds: “It’s a big-stakes story that really feels like a two-hour movie."