My youngest daughter, Scout, is a huge Doctor Who fan so she decided early on that she wanted to be the Tardis for Halloween this year. She wore it last night to a Trunk or Treat event, and will wear it again on Halloween night. Everyone loved it!
We bought an adult blue t-shirt from Walmart, then bought acrylic paint and painted the images onto the costume. We blocked it off with sharpie first, then painted over it. We also found her some blue leggings that were the exact color as the shirt.
Then she came up with an awesome idea for the Tardis light. We took a clear plastic cup and used blue duct tape to mark the lines on it to match the design on the Tardis. Then we took an LED candle and gorilla-glued it onto a circle-shaped light piece of cardboard. We cut a small hole into the bottom (where the candle switch was on), then glued the candle/cardboard onto the bottom of the cup. We then duct taped that onto a blue headband.
The headband was particularly awesome, because you are seen in the dark. I love how it turned out. Hope this helps someone else who wants to be the Tardis this year!