I decided in a Homemade House from the Movie Up Costume, as I love the film and actually saw a little kid dressed up as it last year! It is not an exact replica but I did my best.
I got cardboard from my local supermarket. Being in Art college I have loads of paint and paintbrushes.
I started with the house, which consisted of the box with the top and bottom cut off. I had to give it 2 base coats of white before I cut it, painted it yellow and mint green. I stuck down popsticle sticks as the window frames. The front door and roof had to be attatched separately. Once they were both painted and covered in PVA glue, they were quite hard. I attatched them using super glue to the house.
I bought 10 helium filled balloons for ten euro. Then attached other non helium balloons to the house. I cut out arm holes, waited for the entire thing to dry and TADA, my costume was complete!