Alternatively, paint a refrigerator box.
This is the cardboard stand-up TARDIS available for $225 pre-order from Urban Collector. That's a lot of money for cardboard. It's for people who don't have the carpentry skills to go to Home Depot and build one out of wood. Still, this one will look great in your living room, at least until a drunk friend stumbles into the thing and crushes it. Then you'll have no choice but to grab a kitchen knife and find out how it feels to stab someone. SPOILER: Weird.
Thanks to lilco, who built a time-machine out of an old dryer. Awesome, crank that thing to permanent press and send me back to the age of dinosaurs.