At the beginning of Emergency, officers Reed and Malloy from ADAM-12 make appearances, not an uncommon thing for a new or spin-off series. I don't remember if the events they were involved with for the start of Emergency were the continuation of something that happened on ADAM-12, but it seems unlikely since they didn't air on the same nights. But I'm glad they didn't make a habit of it, like many shows do now.

In somewhat-recent-past years, there were occasional crossover episodes of ER with Third Watch, with Third Watch and Medical Investigation (GREAT show, by the way!) and a few others. But they kept it under better control, sometimes you could even pretty well figure out what happened without seeing the first part, or they did some filling-in-the-gaps between shows like different versions of Law And Order.

And then it got even worse. Shows like Chicago Fire, Chicago PD, Chicago Med... They have crossover episodes that link 3 or even 4 series-es, that of course originally air the same night, but after that... If you're watching any of those serie-es on like ION TV or are binge-watching from Netflix or whatever, you're only going to see one part of a 3- or 4-part "episode." If it's the first part, you won't see what happened later. If it's the last part, you won't understand how it started and how it got to where it is/was. And if it's the middle part, you won't see how it started OR how it ended!

Maybe someday we'll go back to the good old days, like with Emergency!