The letter x is that last letter that prekinders learnt. And needless to say, it's one of the hardest letters to associate a thing with. Usually people would teach x for x-ray but for a phonics purpose it doesn't serve. So we'd take words that has an ending of x such as fox, box and six.
For our craft, we've made the crazy x character with foam eyes and mouths. We've also made fox in a box - what else?!