The outlet stickers have the shadow on them as part of the detail. They are easily available on Amazon

http://www.google.com/url?q=https://www.amazon.com/Electrical-Sticker-Fake-Wall-Outlet/dp/B01AS5TXVI&sa=U&ved=2ahUKEwjl9ID6_c_zAhWlIDQIHUvtATsQFnoECAQQAg&usg=AOvVaw1ldY39toDL5t7JQ6Czi4dq

If you really want to prank people, take a few stacks of there to an Airport and go crazy.