How to cut someone hair without them knowing?

Here's an unltimate plan.... First make sure they are sleeping and sneak into their room make sure u have scissors and before you cut their hair get vasaleign and put it all over their doorknob so then if they wake up and see you cutting their hair then you can quickly grab the outside doorknob and shut the door and they wont be able to open the door because it will be very slippery oh and if u can take a picture lol

They're going to find out when they see their hair is missing.

You don't punish someone by cutting their hair.