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DIY: BMO & Fionna Sword from Adventure Time

This year the BF and I are dressing up as Finn & Fionna from Adventure Time for Halloween.  I decided to get creative with my props and went to town with cardboard and tempera paint.  Here are some step by step pictures of the process for making my pink Fionna sword and BMO!

Materials Needed: masking tape, scissors, primary tempera paint colors, paint brushes, pencil, black permanent marker

Fionna’s Sword

Fionna from Adventure Time has a pink sword, but after realizing that it’s not sold anywhere in stores I decided to make my own.  Luckily, we have a lot of cardboard on hand from our monthly CSA vegetable box.  Making the sword was easier than expected because last month’s box came with vertical inserts.  I trimmed the end of one insert into the point of a sword and cut triangles along the side for details.  For the hilt, I trimmed down the other vertical insert and then made a slit in the middle until I could slide the “blade” through.  Aim for a snug fit, but don’t be too worried if it’s loose, the paint will dry the sword in place.

I only had primary colors, so I mixed white and red in a bowl to make pink.  Note that you only need to add a few drops of white to a primary color to lighten it up.  I also added a drop of blue because red and white made a Pepto Bismol pink.  Dip your brush and paint!

The sword needed about two coats of paint.  I’m sure I could have primered the coat white but it was a warm day and it dried pretty quickly to allow for an extra coat.


To make BMO I had to trim a pre-existing box into a smaller shape.  I carefully lined the edges of my new box with masking tape.  I mixed green, a few drops of blue, and a few drops of white to get his teal color.

I reaaaaaaally should have primered this box white, especially because it had writing on it, but I got super lucky that it was warm and the coats dried fast, allowing me to do multiple coats.

After BMO’s initial teal coat dried, I added a few more drops of white paint to the lighten the mixture for his face.  I then outlined his buttons with a pencil.  Because I didn’t primer, the buttons did need a few coats.

BMO and Fiona’s sword drying.

When it came time to outlining the buttons and detailing BMO’s name on the side, I used a permanent black marker.  It was super easy to work with and wrote on the dried tempera paint really well.

And there you have it!  BMO and Fionna’s pink sword using tempera paint and cardboard!

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