We have such an amazing talent and generous artist in Wolfdreamer when it comes to yarn art. She offers free patterns for a bunch of kid (and adult) favorite characters. Check out her website here.
Last year I took on the challenge of crocheting a Sonic the Hedgehog from her awesome pattern. It was so fulfilling to create something COOL that you couldn't buy in a store. My youngest son, a huge Sonic fan, was beside himself with joy when he opened his new plushie Sonic for his birthday last year and still sleeps with him. You can see my version and my variations here. A year later, as another birthday approached, he asked me for a Super Sonic. As his love for the speedy hedgehog had not waned, I couldn't resist. He was so fun to make.