The Animal class is the classic example of class inheritance for a number of reasons.
First, there are obvious ways to extend the underlying animal class. You'll likely start with sub-classes such as Mammal, Bird, Crustacean, etc.
Some classes, such as Mammal, will extend Animal by adding attributes that are fairly obvious ("Warm-Blooded", etc.).
Other, more problematic, issues that are quite common in developing a class hierarchy are quite obvious if you illustrate with animal inheritance - and this is a good thing for purposes of explanation. Birds fly, right? Well, not all birds... So, how do you represent flying? There are, of course, classic solutions and a wealth of discussion information online about how to solve the problems and tradeoffs that each solution introduces.
Thus, I would highly recommend using "Animal" as your example because of the richness of available information and examples.
