Tanuki udon is broth noodles usually prepared and served hot, but during summer, it can be prepared cold. Cold noodles are popular summer time lunch in Japan.
A tanuki is a racoon dog for Japanese, but tanuki udon is free from racoon dog meat. It is actually broth udon noodles topped with crunchy deep fried tempura batter. And it seems that no one knows for sure why it bears the name of a raccoon dog.
Deep fried tempura batter, which is called tenkasu or agedama, are byproduct of tempura, and often discarded. However, some people, including myself, intentionally make those deep fried batter, using leftover tempura batter. They are often sold cheaply in Japan at grocery stores.
Tenkasu or agedama can be added on top of udon, or mixed in okonomiyaki and takoyaki. They add flavor, crunch, and fatty texture.