Oh man...Foopets! Seeing this thread reminded me of my grief! *Soft, virtual sobbing*
E-Chat.co. It got shut down because it was full of creeps, and although I met some people that turned toxic in the end, I also met some genuinely nice people. For a while, the page said it wasn't permanent and it would eventually reopen, but now it's just gone. After it said that for 4 years.
Omegle as well, which got shut down for similar reasons. But I came across Emerald Chat, which is a nice substitute.
HTFSocial(back when I first joined it in early 2010s, It's the most toxic place online at the time where most of it's people hate or lolcows me until I got banned for no good reasons, and it's people doesn't talk about Happy Tree Friends. and it's shutdowns in 2014,
I used to spend a lot of time on sites that let you adopt digital pets but the only one I remember rn is Valenth, and you didn't really do much with the pets.