Magic Mugs

I have been lookign for different ways to make my mug a little bit different, it needs some unique quality to make people want to but it and contribute to the woodland. One way I have thought about is to use a magic mug affect where the image is concealed until hot water is put into the mug, when the head reveal the hidden image. This could work really well with the seasons concept hiding which season you have until the heat unveils the images. I have found a video link to show how they are made which is really interesting and much simpler than I thought.