This tree is obviously not a bonsai, however it is a good example of a trunk fusion. I saw this tree in our neighbors trash about 15 years ago and was fascinated by the braided trunk. The tree had root rot and only 6 leaves hanging on. I took it home, cleaned it up and nursed it back to health. Today this braided Ficus is about 8 feet tall and in good health.
Four trees were braided together leaving gaps big enough for me to stick a finger through. Today those gaps have closed and considerable fusion has taken place. The tree outgrew our small house and we gave it to friends who had a large sun room that provides the perfect environment.
The thin fine bark of Ficus does not hide scars as well as a heavily barked tree like Dawn Redwood. Something to consider when selecting material for trunk fusion. Below are some pictures of the tree. Click on the image to get a closer view.