Just don't forget these are living creatures that age (well, MOST of them I'm sure) and grow like any other creature. A lot of people somehow forget that the pokedex height/weight are not absolute values that apply to every single pokemon for each entry. They are averages.
That's probably because Furret is 5'11'' long, and the Pokedex shows the size comparison by making the sprite that tall. Even though it would actually only be that tall if you were measuring from head to tail.
Song of the Day: Battle for Freedom FFXII http://www.youtube.com/watch?v=8PjEN-zFlDQ