To make the magic pumpkin all you need is a foam craft pumpkin (we got ours from a Rite-Aid or a Walgreens for under $15) an arduino compatible board (I used the Pro Trinket 5V) and some creativity.
First write the code for the pumpkin. Here's a link to the GitHub for the code, I'd post it here but it's especially long.
Code for the Magic Pumpkin
Feel free to alter any and all of the patterns, all you need to do is play around in the neoPatterns class and change anything you want. Grab a neoPixel ring, a resistor, and plug them into an Arduino compatible board and you're ready to go.
Design and cut out your foam pumpkin as you would a real one. The benefit of the foam pumpkin is it won't rot and there's no moisture to potentially muck up the electronics.
You're going to want to put some discrete marks at the bottom of the pumpkin to make alignment and a nice tight fit easier. then take the double stick off the breadboard, place it on the bottom of the pumpkin and ease it into the body of it.
There you go. This is a great project to do with kids or if you have an extra hour or two. Also because it's so quick it's a nice last minute decoration. Thanks for reading, keep on making.