We made this simple Tardis from a cardboard refrigerator carton and some paint. Hopefully you can make it for under $20, less if you have existing paint.
The items you'll need:
Fridge carton - Free from a large electrical appliance retailer. Larger the better.
Paint - Blue for body of the box. Rattle can black and silver for the details.
Roller or brushes.
Printer - to print out the signs and windows.
Step 1: Box and Blue Paint
Enamel gave us a nice glossy finish but took a full day to dry.
Step 2: Stencil the panels.
NOTE: Spray very, very lightly. Even the lightest spray will show up, and you can always add paint later.
1. Using cardboard stecils do the black first. You need a single panel at the top and then 8 panels in two rows.
2. Next do the silver highlight. Moving the stencil up and to the left of the black, only spray along the bottom and right of the stencil.
Step 3: Signage
The windows were simply copy paper with Sharpie lines, and then glued on.
The other signage was printed and glued on. The images we used are included here.