Hi everyone.  First off, I'm a complete beginner to these games.  I followed Demon Souls with a lot of interest but always held off on jumping in; I would have probably done the same for Dark Souls had the Quick Look not completely sold me.  I'm also going sorcerer for my first attempt at this, with the knowledge that that's probably a terrible idea.  I realize that the time I've spent in the game is so small that it shouldn't even count, but so far I'm really enjoying it, that is when I'm not agonizing about the permanent loss of the measly handful of humanities I've been able to gather.
 
I was in the Undead Burg tower right before the Taurus Demon, and when I rolled through a bunch of barrels out came what I can only assume what was Crystal Gecko, not that I've ever seen one.  I was pretty taken aback at seeing one so early in the game.  There wasn't much doubt it had noticed me, as I had rolled right over it.  I was expecting it to run away, but instead it started to waddle off pretty slowly.  I targeted it and started to follow behind.  It went down the stairs, and for a brief moment it moved out of my line of sight as it went to a lower level.  Of course, once I walked those few steps to where I should have seen it, it was gone. FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF 
 
 So, I have some questions about those geckos.  First, is their appearance random?  I'm guessing that it is, but I won't complain if it's there in a future playthrough.  Secondly, is their rarity and usefulness the exact same as it was in Demon Souls?

Anyway, I'm not completely brokenhearted, as this sort of experience was pretty much what I was expecting.  Earlier I had found both a shard and a chunk of Titanite, so I was actually foolish enough to get my spirits up. 

@SpaceRunaway: They are not random, and if you don't manage to kill it it'll appear the next time you're there after a world reset (bonfire). So no sweat. :)

as far as I know they are not random, and what you get from that one isn't very hard to get as you progress further in the game.

They appear in specific places, and will keep respawning after a bonfire visit until they die.  Of course, you might be like me and require quitting to the main menu and reloading to get it to appear.  My game is weird like that.

Fantastic! Thanks for the quick replies, back in I go!

They seem to run to a specific spot each time and if you don't kill it before then they do a little chant and teleport away (I suppose it's supposed to be them turning invisible but whatever) I'm guessing you'll always get a single Twinkling titanite from it, but on one of my characters I actually got two as well as two more regular shards and I didn't even have any Humanity at the time :D

geckos respawn now on a new save / load or some such effort , they used to disapear for good , only respawning if you killed a boss , now they respawn but only can be killed once . also the fog ring , or hidden body socrcery work wonders in sneaking up on them , if you dont run or roll while cloaked you can walk directly next to them before you start unloading .. without this spell/ring you will probably miss half the geckos in the game as they will see you and run before you even notice them.

they pretty much always drop twinkling titanite and another random shard , but they are alot less important now so dont worry if you miss them , near endgame you have alot more farming choices with enemies in the last area dropping chunks of each color , and the shortcut to lost izalith for farming demon titanite, dragons in valley of drakes for dragon scales , and i swear there was another end game critter that drops twinkling titanite.

also as far as i can tell the gecko hiding in the barrel in undead burg is THE ONLY gecko in a barrel in the entire game , and theres also very few items hidden in destructible objects .. apart from the corpse-in-a-jar situation

@envane: well, according to what I've read you can trade the anti-bleed and poison stuff from the garden for twinkling titanite with snuggly. Sure it's abit inconvenient, but sorta overly easy to farm :P

@Ares42: you can only trade those items once per game tho . so its a limited supply