Making animals and fun shapes and pictures with the food in the boxes are an old tradition and many Japanese mothers compete with each other to make the prettiest food displays for their children's lunches. The boxed lunches are making their way into other countries as a way to make healthy food more fun for children. Processed foods are rarely included in bento boxes.
Here is a gallery of Bento Boxes: Air and Angels
And here are galleries of fun food displays (Really, check some of these out!):
Bento Box Art
Henny (Scroll down a bit)
Onigiri are rice balls which are typically wrapped with nori (toasted seaweed) and lightly salted. Some onigiri have fillings or are sprinkled with spices. We were going to eat them all by ourselves, so we only used 1 cup of rice.
After the water had evaporated completely, we flipped the saucepan upside down (we did this over the sink, not trusting ourselves,) and held it that way about 3 minutes.
We placed a peice of plastic wrap over a glass measuring cup.
We then scooped the rice into the plastic wrap. We picked formed the plastic wrap into a satchel shape and molded the rice through it into triangle shapes. Test it to make sure it isn't too hot to handle-ours cooled quickly.
We cut nori (toasted seaweed) into one inch strips with scissors. Nori is available at most supermarkets. We wrapped on strip of nori around the bases of each rice ball.
Finished rice balls. These were yummy. My sister liked them but thought we put too much seaweed on them.
There are much more detailed instructions on making onigiri at Just Hungry.
*Please forgive the photo of me, that's what you get when your sister wakes you up after you have gone to bed sick and says "I'm making rice balls!" and when you say "Good, have fun!" and roll over, she starts with the puppydog face and "I thought you were going to help me... I can't do it by myself..." I am feeling much better today.