I remember the original Metal Gear Solid's anti-piracy measure was having Meryl's codec number on the back of the box. The game would tell you (the player, not Snake) to check the back of the box. I actually had no idea what it was talking about and spent ages checking my items and calling people. Eventually I gave up, but I happened to end up looking at the box at some point and noticing the codec screenshot on the back. The game forcing me to have that realization that it was speaking to me and not Snake opened my mind to more of the possibilities of an interactive medium. That and Psycho Mantis.
Also, interestingly, my Auntie and Uncle had a chipped PSOne at the time and a bunch of copied games, MGS being one of them. That part with the codec totally stopped them from getting any further. So it actually worked. Guess that's what the world was like before everyone used the internet.
That's not entirely true, and I would know because it was years before I realized that the CD case Campbell tells you to check was the game case and not the floppy disk you get right before that particular codec conversation. If you approach the doors that you need Meryl to unlock for you without ever contacting her yourself, then she'll call you, the game progresses as normal. A lot of people think that the game just ends there if you're too dumb to check the back of the box, but since I'm pretty dumb I can confirm that MGS does in fact throw you a bone.