Guidelines
There are three types of entries that make this pool work:
Type I - characters casually reveal their animal side. Typically played for laughs.
Type II - characters make use of their attributes for situational purposes.
Type III - characters grow unhinged and release their animalistic nature, whether it is by intention, impulse, or rage.
Exceptions
To address the possible misconceptions as to what entries are credible:
A. No "full" transformations (i.e. animalizations). The ideal of this pool is the artists' focus on the characters' emotions leading to their transformations. Also, animalizations are often used for simple, comedic, or symbolic reasons.
B. Unique species such as vampires and oni are a tricky case because they are capable of using their instincts while sane. What would make them credible is that they'd have to be Type III, acting by pure rage or blood impulses.
C. Much of the Youkai (without noticeable features) in Touhou's cast are rarely portrayed in any feral manner. Such art that does exist are usually Type III.