Take for example CSI NY and Without a Trace, WaT crossovers over with CSI, CSI spin-offs Miami which spin-offs off CSI NY, so logically WaT is set in the same NY as CSI NY, and yet it never makes mention of the CSI NY "Cabbie Killer".
I once took a year-long screenwriting course in college, in which we'd all read each others' scenes aloud. I was writing a rom-com, with the last scene being a wedding. The teacher was reading my narration bits on that final day, and she got a special script the other readers didn't, and thus read aloud the part where the protagonists from all the other
scripts stood waving and cheering as my
Minds were blown.