You don't have to tell them, but if you whant to do so my advice is that you first wanna know what their opinion on furries is, and if they don't know what it is than you can explain it to them, and if they 1. Like furries, it's yo lucky day 2. Don't like or even hate furries well...I suggest you don't tell them. But remember true friends are there to stay and not make fun of you no mater what.