When Jesus was talking about false teachers, he said that by their fruit ye shall know them. If we broaden the topic we could be talking about anyone who pretends to be something they are not for the purpose of ill intent.
When I was about 8–10 years old I had a friend that had an older brother. The older brother was mechanically inclined and used to talk me into bringing some of the bikes in our garage over to his house. He would take them apart and mix the parts up and make ridiculous looking bikes. He made me think that I looked really cool riding on those bikes, but he was laughing at me the whole time. At first he pretended to be my friend; he was subtle about the whole thing. Then, as time went on, he grew tired of the sheep outfit and was blatantly not my friend.
Sooner or later, what’s down in the well comes up in the bucket. The wolf is going to forget to bleat and let out a howl.