Practical joke of the day

Note - if you get arrested for this, please send me a text message so I can delete this post, leaving you completely screwed.

Requirements:

1 x Digital Camera
1 x Printer

Plan:

Go to the house of a friend (or enemy), get up close without being seen, and take a photo of their front door (with enough of the house showing to make it clear what the photo is of). It's fairly essential that there's a number showing on the front door.

Go to the house of a stranger, get up close without being seen, and take a photo of their front door too - same rules apply.

Go home, and find out the postcode of each address.

Print out two copies of each of the pictures of your friend/enemy's house, and write their postcode on the back of one.

Print out two copies of each of the pictures of the strangers's house, and write their postcode on the back of one.

Take the copy of the photo of the friend's door, with writing on it, and pair it with the copy of the stranger's door without - then stick both of these on the front door of the stranger's house.

Do the same with the remaining two photos on the front door of your friend's house.

Wait.