Big Man is a Birthday Cake, Halloween, 2005
He wanted his costume to be a chocolate birthday cake with pink icing.
I found a large box, and used a serrated knife to cut out most of the bottom and a hole in the top big enough for his body.
For the straps: I measured and cut four lengths of duct tape, put them together sticky side to sticky side, then secured them to the inside of the box with more duct tape. I did this while he was standing holding the box up, so that the straps would be comfortable and functional. They cross in the back.
He wanted a chocolate cake with pink icing, so I scrounged up some leftover brown spray paint and mixed together some interior semi-gloss to get that rather vile pink. White caulk doubled for decorator's icing - it was just like using an icing pen from the grocery store. That's self-adhesive weatherstripping simulating icing oozing out from between the layers.
The only problem with this costume was that it came down past his knees. Walking was no problem, but we live in a neighborhood with high front porches, and the poor kid couldn't climb stairs in this thing! Luckily, it lifts off and drops back on easily with a grownup's help.