Cause he's a dog.
A Bark-aeologist
Ruff Bark
Because the chicken hadn't evolved yet.
Because it was a lame joke.
A Christmas-Quacker!
Roost beef!
Cause it was invented in Alabama! Inspiration came from the comments(http://mobile.reuters.com/article/idUSKBN0GP1NS20140825 irpc=932)
Cause if it was invented anywhere else it'd be called a teethbrush.