So I finished my younger son's Sonic costume and our October has been so busy he's worn it three times already and it's not even Halloween yet! I used a basic Simplicity fur suit pattern as the base pattern for the hood and shoe covers. The top is a sports top from Target I cut the sleeves off of and sewed flesh colored sleeves and the tummy patch onto. The bottoms are just a pair of elastic pants I made by patterning off of a pair of his sweatpants. The hood is made of fleece, the spikes are stuffed with polyfil and boned with plastic boning to help them stick up. The shoe covers are from two remnants of vinyl backed with a layer of iron on batting to make them puff up a bit and the gloves are purchased.
I'm pretty happy with how it turned out - it's comfortable for him, he can see and everyone seems to love it.