FK

Stands for "Fortnite Kids"

Kylie: I just joined the FK community!
Jacob: we're done

back at you

a phrase to use when you want to give back the insult to the person that insulted you

John: Your hairline is so crooked.
Betty: Back at you!

slenders

a type of group in roblox aka. slenders, dressed up as sometimes fully black or half black half white, described as a mean and grumpy person

some random user: hi
Slenders: oh hey what's up, you look like u don't have a collarbone and ur so ugly, kid poopy poopy kidd!!
some random user: u so meannn