We recently got a load of drywall shims, which have turned out to be massively useful in kiddy crafts. This craft was so easy peasy and the kids loved the end result.Each one got to decorate a cardboard shim with pens and stickers and then I cut each shim into three pieces (two equal length and one slightly longer). I stapled the shorter two to the longer one to make a kind of pinafore top and then hole punched the to ends of the chest piece and tied on string to make a bow fastening.Then I just cut lengths of dollar store crepe streamer that we had left over from the pirate-superhero-mermaid party back in September and the kids danced around like silly bouncy things in the dresses.Of course eventually they figured out they could pull off the streamers and make headbands and wave them around, but the bodice is sturdy enough that we can keep it and just stick on other streamers another day.
Of course you don't need drywall shims to do this. Any old cardboard will work just fine.