Almost 100 years ago, John Krubsack made this amazing chair by growing a bunch of box elder trees together. What makes this extra special is that he figured out how to graft the trees together as they were growing, so that they naturally formed all of the joints to hold it together. The whole thing took about 11 years to grow. In this age of rapid prototyping, I can hardly imagine spending that long on a project. It just might be possible, however, to make a miniature version for a mouse out of some brassica rapa plants.
Oh, and if you are looking to raise your own furniture, treehugger has some plans to grow
a three-legged stool.