This year Minnie's going to be the 12th Doctor - with a somewhat William Hartnell inspired costume however with a feminine touch. (There's a feathery trim on her black cloak.) And I'm going to be the TARDIS (Time And Relative Dimensions In Space).
Pretty much just put together what I could find and made some stuff. The hat, mostly. Dyed a white hat blue, then used felt, cardboard, ribbon, a water bottle cap, and a plastic drinking cup to make the light. I also have one of those battery operated lights that go into Jack-O-Lanterns instead of a candle underneath - the cup is partly sewed, partly velcroed down so I can raise it up and turn the light on and off.