I had some once, they were tamagotchi connection, I believe the first ones that were able to interact with each other. I used to pair them up to breed, but without fail the generations would alternate between opposite genders and same gender each time, weirdly uniformly so it didn't always work.
Those things were frickin expensive but I remember how hyped up they were, and I saved up my birthday money to get them. They were not really worth it based on what you were able to do with them. But it was neat how they changed forms, and you could go visit your current tamagotchi's grandparents by connecting to the internet.
I was one of those who had the original Tamagotchi (got it as a present) as well as one from the first Tamagotchi Angel series.
I had a few Gigapet ones as well, but I remember preferring Tamagotchi because there was a way to put the pet on "pause" by going into the settings menu to adjust time (which was superhandy since digital pets were banned from school).
My brother owns them now. On the Angel Tamagotchi he somehow managed to get one of those poop-based special ones.