Combining the LAW & ORDER shows together for a cohesive crossover will be quite the feat, but dream pairing number 1 is the writers managing to get three of the franchise's biggest titans together. LAW & ORDER star Sam Waterston has been a part of the world off-on since '94; Mariska Hargitay and Christopher Meloni joined in '99, with Hargitay notching an astonishing 23 seasons (and counting) on SVU, with Meloni appearing for a dozen seasons on SVU before headlining OC in '21. Fingers crossed the writers can find a way to get the trio in a scene together, even if it's just a beat at the end. (On the last major ONE CHICAGO crossover, a scene was crafted for P.D.’s Voight (Beghe), MED’s Goodwin (S. Epatha Merkerson), and FIRE’s Boden (Eamonn Walker) to close out the event, but it ended up being cut.) (Photo credit: NBC)