I still have mine as well. There were actually two variations, one was for the original gameboy (the blocky one that took 4 batteries) and one was for the Gameboy Color. They had different trading ports on them, and I was the only kid in school that had a cable that could link them both together. Also, the gameboy color trading port was the same as the gameboy advance trading port. But, the generations (Gen1 and Gen3 OR Gen2 and Gen3) couldnt link together (Gen1 and Gen2 could though). You could use the same cable to link two Gen3's together though.
Trades happened a lot at my school. It happened so much that we discovered that if you unplug the cable at a specific time in the transfer between a Gen1 and another Gen1 the pokemon would transfer and be kept at the same time, but one person would lose their pokemon. I forget the exacts, it has been almost thirty years lol.
There was also a lot of talk trading between Gen2 and Gen1. Lots of rumors about getting pichu into Gen1, and steelix, but obviously, nothing every came from it other than kids being kids and spreading rumors.