I am sure you all have seem them in plenty of anime's. But may have been unaware of what they are called. Well you guessed it those cute anime girls with the animal ears and tails are called Kemonomimi. Kemonomimi meaning animal ears. Kemonomimi characters normally appear for the most part human with some animal traits like Horo from Spice and Wolf pictured above and below.
Horo is considered okamimimi > Wolf
Then we have the common nekomimi > Cat
usamimi > Rabbit
inumimi > Dog
kitsunemimi > Fox
You will find more but that covers what you will normally see.