To make Boxy, buy a normal chao, and give it skel dogs, then give it a cardboard box to wear on it's head, then make it a Hero/Swim/Power.

 

Eggy

To make Eggy, buy a white Chao, and give it skel dogs, then give it a normal Chao egg shell to where on it's head, then make it a Hero/Swim/Power.