September 1989 - January 1, 2005
NAME ORIGIN
From his color.  (Obsidian is shiny, black volcanic glass.)
Other given names considered:  Rafael, Elijah.
NICKNAME(S)
*Sid*, *Weasel*, *Weas*, Sid the Weasel, Weas the Beas
He was also accidentally called Whiz, Wizzle, Fizz, and Sleaze.
He was a long, slender, pointy cat and because of this, I called him Sid the Weasel one day and it stuck.
DATE OF BIRTH
September (?) 1989
PHYSICAL DESCRIPTION

Long, tall, and slinky, but not at all heavy.  He never weighed more than around 9 pounds (4 kg) and despite being on steroids for years, he never gained weight.  A lot of people would kill to have his metabolism...  In his later years, due to age and illness, he was unfortunately quite underweight.

Weas had a remarkably expressive face, and our favorite of his facial expressions was a combination of alarm, confusion, and curiosity that involves him flattening his ears, flaring his nostrils, and frowning all at once. 
He was solid black except for a patch of white on his chest and a white spot on his right front paw that looked like it was dipped in paint.  He had the longest whiskers I've ever seen (rivaled only by Andromeda's).  The longest ones measured about six inches (~15 cm).
MEOW
Very loud and somewhat Siamese-sounding.  He meowed frequently - and sometimes incessantly - often for no evident reason except perhaps to hear his own voice.
PURR / BISCUITS

Purr:  Moderately loud to very loud.  Frequent.
Biscuits:  Made moderately vigorous biscuits when very happy, usually while standing up.
HISTORY

Weasel was brought to the Animal Hospital at which I used to work by a lady who found him lying by the side of the road.  He had been struck by a car and there was severe damage: muscles, ligaments, and tendons had been sheared away from his femur and pelvic bones.  A vet repaired the damage as best she could, but figured he'd never walk normally again.  Someone forgot to tell him that, however, as he was quite athletic for the most part, though sometimes a bit clumsy.

The lady who found him was not able to adopt him, though she wanted to, so he stayed at the hospital for a while.  I used to sit on the floor in front of his cage and he would creep out and curl up in my lap and purr.  He seemed like such a sweet, polite guy. 
One morning, I asked one of the vets what was going to happen to the "little black cat" and he replied that kitty was headed for Animal Control (aka the Pound) later that morning.  He went home with me instead.  A vet estimated he was around a year and a half old, but he must have been closer to ten months, since he grew quite a bit after he came to live with me.
PERSONALITY

Very affectionate, often to the point of being clingy.  He frequently followed me around the house meowing until I picked him up and petted him.  He was a great lap and bed cat.  He was, however, terrified of everyone except us.  Many of our friends and family members never saw him.

Weasel was not the world's brightest cat and it didn't take much to confuse him, but we can't all be geniuses, I suppose.  He was a natural comedian - whether he intended to be or not - and gave us more laughs than any other cat we've had.  He routinely roamed aimlessly around the house, changing direction when he encountered an obstacle.  Watching him reminded me of observing paramecium move about under a microscope in a college biology class.
Weas was our oldest cat for some time, but only chronologically.  Mentally and emotionally he remained quite young, and until the very end, he acted like it most of the time, running around the house like a maniac and playing tag with the other cats.  The local wildlife must be grateful to us for keeping him inside, since he was a top-notch hunter.  A few mice who strayed inside found this out the hard way.
MEDICAL CONDITIONS
A mystery illness; pancreatitis (probable); possible damage due to trauma; another mystery illness; kidney failure.  See Details.
HOBBIES / INTERESTS
Meowing, curling up with other cats, running up and down the stairs at top speed, licking my knees when I stood in the kitchen, and urinating on the firewood (we all have a few bad habits).
FRIENDS
Weasel got along with all the cats the majority of the time, but was closest to Irene Adler and Sasabe.
SCARED OF THE VACUUM CLEANER?

Mortally terrified.