Via Pharyngula, here's a wonderful post examining the evolutionary history and physical design of cats. It even begins with some light verse:
Felus Catus is your taxonomic nomenclature.
An endothermic quadruped, carnivorous by nature.
Your visual, olfactory, and auditory senses
Contribute to your hunting skills and natural defenses.I find myself intrigued by your sub vocal oscillations.
A singular development of cat communications.
That obviates your basic hedonistic predilection
For a rhythmic stroking of your fur to demonstrate affection.A tail is quite essential for your acrobatic talents.
You would not be so agile if you lacked its counterbalance.
And when not being utilized to aid in locomotion,
It often serves to illustrate the state of your emotions.Oh Spot, the complex levels of behavior you display
Connote a fairly well developed cognitive array.
And though you are not sentient, Spot, and do not comprehend,
I none the less consider you a true and valued friend.
What's better than a poem written by a fictional android?