Board Thread:Questions and Answers/@comment-36601361-20180915183450/@comment-34740270-20180915221132

They are, in fact, dog ears. A "Temmie" is a four legged creature, that seems to be a cross between a dog, a cat, and maybe a human, because of their ability to speak. However, other monsters (such as dogs) can talk in the Underground, so Temmie might be cat and dog, or a species of it's own.