It is Furbys for sure.

Even though it looks wrong, 'Furby' is the official name so Furbys, Furby's etc is used. However, in a German product, they do use 'Furbies' but that seemed to be a one-off thing.

God I was waiting for someone to make a poll about this like god-

Theres a page here that explains it better.

I would say both are correct, since Furby is an own name (and so the plural would be Furbys) but then again, gramatically Furbies would be correct.

I personally prefer "Furbies" but "Furbys" is the official term.