This Halloween was our six month old baby's first Halloween, so we knew that we had to start her off right. It took months of brainstorming and polling people, but finally I thought up the perfect costume for her which we were able to keep a secret ...
The Tardis from Doctor Who -

Complete with her very own Doctor, the 10th Doctor David Tennant!

The photo is dark, but I assure you, the suit was navy blue, the shoes were maroon, and the tie was burgundy.
I made the Tardis and the sonic screwdriver, all from scratch. The Tardis is not the most current one because we realised pretty quickly that my husband could better pull off David Tennant than Matt Smith, so we matched her to her appropriate Doctor.

Also, the Tardis is to scale! I figured out how wide it needed to be to be comfortable on the baby, then did lots and lots of math to scale everything else down properly. There were some structuraly things that I had to omit to keep it from being too heavy on her.
My husband cobbled together the Doctor's costume partly from his own wardrobe, and partly bought things - like he had to buy the proper shoes. The Physic Paper was a small leather wallet with white card inside. I was most impressed that he shaved off his whole beard for the costume - now that's commitment!
Here is the Tardis foam interior, and some of the vinyl cut-out pieces:

and here is the Tardis without the baby inside - this gives a better detail shot. You can see the arm opening on the side.

I have to say that it took a lot of trial and error to see what she would be comfortable with but in the end it was worth it as she wore the Tardis for over an hour with no complaining.
The Sonic Screwdriver was really fun but also a pain to make. In the end, it took:
* a dowelling rod and some other bits of wood
* a brass plumbing fixture
* a fake pearl bead
* a bit of flat acetate
* a black drywalling screw (it should have been a drill bit but I thought it a waste to buy a brand new drill bit then make it unusable for one night, so instead I reused a drywalling screw)
* a flat marble (we couldn't find a blue one, so I coloured the back of a white one blue with a permanent marker before attaching it)
* acrylic paint
* silver paint
* brown marker
* electrician's tape
* and a glue gun

and some reference photos:


and me? I don't really look like any of the companions, so I was Amelia Earhart. The story goes that the reason that I went missing is because the Doctor showed up one day and whisked me away with him. The leather flying helmet is vintage from 1915, but I made the goggles from a broken plastic container, some leather scraps from a jacket that I'm altering right now, and a little buckle.

Needless to say, they were a huge hit at the Halloween party! It was also very obvious which others guests watched Doctor Who - when fans caught sight of the Doctor and a baby Tardis they just freaked out.
Thanks for looking, and don't forget to vote for your favourite costume in the contest!