
it's an electronic toy that was very popular among 2000 kids, being pretty much the predecessor of the "Pou" mobile game. It was a tiny round egg-shaped device no bigger than a keychain wich had a tiny pixel creature living inside. You were supposed to carry it around, feed it and play games with it during its lifespan. (As an example, the girl from Turning Red disney movie has one attached to her backpack).
The joke in Sunny's comparisson is that if you didn't feed your tamagochi or neglected it for too long, it would pass away (although it was always bound to die due to old age anyways, and then you would just hatch a new one) so Sunny feels like it's being taken care of like a tamagochi lmao.
As a side note I remember I got real dependent on my tamagochi as a child, to the point of obsession. Once I left it at home when I went out to a restaurant and when I came back there was a literal circle with angel wings floating on the screen (meaning it died) and I cried SO MUCH
the funniest thing is that they're currently doing it in the raws lol. It's all bc sunny isn't of legal age yet,,, they literally waited till 23:59 on new years eve (in korea ppl used to legally turn one year older on January 1st) to start making out lmao.
Also he said he's a tamagochi