Roundcats are cute (and huge) cats that come from super doomspire, a game on roblox.
You can play a mode called Roundcat Rally in a public server; it basically consists in defending your roundcats by building walls and blowing up the opponents' roundcats.
On Roblox egg hunt 2020 (Agents of the E.G.G.) The roundcat egg was released. It was an alternative way to represent the roundcats.
You could earn it by getting 30 eggs that dropped when you killed someone.
Me: hey dude wanna play super doomspire?
R. Friend: sure let's play the ROUNDCAT rally mode!
Me: Ah well I have the roundcat egg on my head so I can definitely win.