They look SO real up close. They used to have you bite a styrofoam cup and send it in and they actually make them custom to fit your bite radius perfectly.
I used to go to bars with friends and I would pretend to be alone and try to keep my mouth closed until I could sidle up to nice looking girls at the bar, and then when they least expected it I would sit right next to them and smile at them, and start pretending to hit on them. My friends would die laughing watching their reactions from across the bar. It was one of my favorite things to do when I was first married, and we still went out a lot. The hardest thing was trying not to laugh, because they would realize something was up, and you wouldn't get their natural reactions.
I had an employer (this is where I found out about Dr Bukks) who was the master of getting rid of unwanted solicitors by wearing them to greet them. Priceless.