You can change your friend’s profile pic into your WhatsApp on your mobile only but not globally .
  1. Choose a funny profile picture for your friend.
  2. Resize the image to 561×561 pixels and name it with your friend’s mobile phone number.
  3. Save the image in SD card -> WhatsApp -> Profile Pictures.
  4. Overwrite an existing image if required.
  5. Disable WiFi and data network. If you don’t WhatsApp will automatically update the picture.
  6. Now show it to your friend who’ll surely shocked to see his changed image.