DIY Blue Shell Costume (From Mario)

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Learn how to make a DIY blue shell costume for kids, adults, or dogs. The blue shell from Mario Kart is a fun, unique, and simple Halloween costume.

Since my husband and I did Mario Bros inspired costumes (Toad and Princess Peach), we wanted to pick a Mario inspired costume for the dog. We went through a couple ideas, but we finally decided on a blue shell costume since it would be easy to make and easy for the dog to wear.

I had so much fun making this costume, and it was quick and easy to make! I was able to use my free spike/horn template I’ve used for other costumes which made it easier and is available to you. I’m so excited for the dog to walk around with this fun blue shell on his back!

DIY Blue Shell Costume (From Mario)

This was actually a pretty easy costume to make since it was mostly painting and gluing, and I only did sewing to change the placement of the straps. The longest part was waiting for the paint to dry between colors!

I started with a costume turtle shell that is made out of foam so it’s nice and flexible, and then I painted it the colors I wanted and glued the handmade spikes on the back. I even have a free template to help you make the spikes!

DIY Blue Shell Costume (From Mario)

What is the Mario Kart blue shell?

The blue shell from Mario Kart is the shell that players in the back get and send it up to hit the player in first place. It’s different than all the other shells (color and capability) in the game, and you love to get it but hate to receive it.

There are a couple of different iterations of the blue shell from the different games over the years. Most of the blue shells have white wings that come out the side, but I didn’t think my dog would be able to handle that. Instead I just did the shell and the spikes, but it’s still obvious to what he is.

This is a dog costume. Does it work for kids or adults?

Yes, this is a dog costume. I moved the straps to work for a dog body, but if you leave the straps where they are (like backpack straps) it’ll work great for a human. You can paint and add the spikes exactly the same as this costume, and it’ll work for a kid or adult.

DIY Blue Shell Costume (From Mario)

Need more costume ideas? Check out these lists:

DIY Blue Shell Costume (From Mario)

DIY Blue Shell Costume


  • Back turtle shell with straps*
  • Blue acrylic paint and paintbrush
  • White acrylic paint and paintbrush
  • Black permanent marker
  • Cardboard
  • 3D Spike/Horn template
  • Hot glue gun and hot glue
  • Optional: sewing tools and sewing machine for moving straps
DIY Blue Shell Costume (From Mario)


Paint the main of the shell blue. Let it dry. Paint the outer edge white. Let it dry.

Trace the spikes onto the cardboard and cut them out. (If you don’t want to use my free spike/horn template, then you can cut 1/4 circles out of the cardboard.) Roll them along the edge of a table to get them curved into a cone. Make enough spikes for each section of the shell.

Glue the spikes into cones. Paint them white and let them dry.

Hot glue the spikes onto each section of the shell. I tried making it so the glue didn’t show, but I was worried that the spikes would fall off so I glued around the outside too. I don’t love the look, but I needed the spikes to be sturdy.

Trace the sections with a permanent marker to get the right look and to separate the white from the blue. You finished!

Optional: take the straps off and sew them on where you’d like them. For a dog I did a small strap that will tie onto his collar and a strap that will tie around his chest.

DIY Blue Shell Costume (From Mario)

If you make something using this sewing project, I’d love to see! Please share it on social media with the hashtag #heatherhandmade and tag me!

DIY Blue Shell Costume (From Mario)
heather sewing

I believe small sewing moments can create great joy. Find your own “right” way to sew. -Heather

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