Costumes · DIY · Sewing

Fancy Firefly Fanny (U.S.)

I say U.S. because fanny means something else in the U.K. Just to be clear, it means butt here in the states.

Now that that’s out of the way, lets talk about this cool butt I made a year and a half ago.  My niece wanted to be a firefly fairy for Halloween and so my sister-in-law asked if it would be possible for me to make the butt of the costume. She found a fairy costume for her to wear online.

I gave it great contemplation and drew some diagrams for my niece to approve. Unfortunately, it was too realistic for her. They found a round pillow-esque butt someone made on Pinterest and showed me. So I took to task and planned out a butt that would  be over the top yet still make her happy.

In this project, I used (some affiliate links were added to be helpful):

  • Mini LED battery powered string lights in white/green with variable settings (2) Link
  • Sage green poly satin fabric to match the costume (1 yard) link
  • Seat cushion foam (1 small) link
  • Fiber fill
  • Glitter ribbon in green and gold
  • Large plastic gems link
  • Pin backs (3 small) link
  • Adhesive velcro link
  • Glue gun and glue
  • Thread, straight pins, and sewing machine
  • Soldering iron and solder
  • Electrical tape
  • Compass and pencil link
  • Large sketch paper
  • Fabric scissors

The first step was figuring out how big to make it. I asked my sister-in-law to measure the circumference of my niece’s bum. I then used a compass to make a circle on a piece of paper roughly that size. I cut the circle out, placed it on top of my foam cushion and traced around it. I cut out the circle and then had my base. In the center of the base, I cut a rectangular hole for the battery pack of the LED lights to fit into very snuggly.  Unfortunately, I didn’t take any pictures during this step, but you can see how the battery pack fits further along in this entry.

Next, I began hot gluing fiber fill to the foam cushion until I had a round ball of fluff that would hold together firmly once covered with the fabric. Once the fiber fill was in place, I moved on to the lights.

I realized that when the batteries were in, the battery packs became quite heavy. Too heavy for a three year old to wear comfortably in my opinion. This is where the soldering iron comes in. I cut the second string free from its battery pack and soldered it to the end of the first string. This was a bit… messy as I’m horrible at soldering and I only had what I had left from soldering a broken laptop ac connector years and years ago. There’s all different kinds of solder for different purposes and I wasn’t going to go out and buy more. At any rate, it worked and I covered the connection with electrical tape. Now she only had one battery pack to carry.


My fourth step was arranging and attaching the lights to the fiber fill. I tried various arrangements (with the lights on) and then when I thought it looked right, I hot glued them to the fiber fill. I then covered the wires as much as I could with more fiber fill so they wouldn’t show through the satin fabric.

Next, I had to figure out how much fabric to cut. So I laid my yard over top the fluffy mound and marked where it reached the edge. I then added a few inches so that it would meet near the center while leaving an opening for the battery pack and also a seam allowance. Using my trusty compass, I created another circle on my giant sketch pad as a pattern and cut out my circle. Sorry, there are no pictures of this process either.


In the photo above I began marking two inches in for the seam and tunnel for the drawstring. I folded the fabric over to meet the dots and began ironing at points so that I could pin the seam in place.

Obviously, since this was round, it was not easy and took a great many pins. Once the entire circle was pinned, I made small cuts so that the seam would lay flat.

Lastly, I sewed it. It’s not perfectly round, but no one was going to see this side of it.


I wrapped the fabric around the base, inserted a string of yarn to use as a drawstring and pulled it closed.


At this point, all that was left was decorating the outside and adding the pins. The ribbon is supposed to represent the segmentation seen on a bug’s exoskeleton. The large gems I used just to make it more flashy/cute. I decided to use hot glue on the ribbon instead of sewing because the fabric was already cut and sewed.


The pins really should have been sewed on, but I tried to glue them and leave it at that.  This was a mistake as they pulled loose. Also, I need to really mention, that when using pins, please make sure that they are attached to the costume before the child is in it and also that they are secure! Some came loose and poked my niece. She was really upset. So upset, she didn’t want to wear it. What I did after that was buy adhesive velcro and take it over before we left for Disneyland. This both did not allow for enough time for the adhesive to “set” and also lay flat and make good contact because of the way the fabric was bunched up from the drawstring. I should mention, the only reason this butt had to be removable was so that it could be taken off for Disneyland rides if needed. Otherwise, obviously, the smart thing to do would have been to sew it directly to the costume. If I had to do it again, I’d do the velcro but sew it to the costume and to the butt. No adhesive.

Moving on, I had some extra fabric and ribbon, so I decided to make a cute bow for the top to hide the connection between the costume and the butt. The bow is also a pin.

And here we have the finished product!


It turned out quite nice. The lights had three settings: on, flash, and slow pulse. The slow pulse was the best, I thought, but my niece liked them to be flashing. Here she is at Disneyland before it got dark:


So what do you think? Pretty nice, right? If you decide to try to copycat this guy, please tag me in your posts. I’d love to see how it turns out. Also, a nod to my hard work would be appreciated and a link back to my blog.

Thanks for reading!

One thought on “Fancy Firefly Fanny (U.S.)

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