The collections section of the bank has slots for 59 different mini pets. Rytlok and 5 others are under a "mini pets (special)" section. So you'll probably see people running around with other mini pets, but the Rytlok one is probably only from the collector's and digital deluxe editions.
Also, in WoW the small pets are stylized so that they look sort of like baby versions of whatever they are. In Guild Wars, they use the same model as the larger version. You could call it lazy, but you also get all the detail of the full size model.
Diablo mini pet in WoW:
Rytlok mini in GW2 (
here's a better shot of the model):
And actually, if you've never played an MMO, even World of Warcraft, that might be an advantage for you with guild Wars 2. With most recent MMOs you have a very linear progression of quests that lead you through each zone as you level up. Specifically I was recently playing the WoW Mists of Pandaria beta and got really bored with the quest I was on. I couldn't skip it though, because without completing it I couldn't get the next quest, and thus couldn't continue questing in that area. I was locked into that quest progression and had to complete every step.
In Guild Wars 2 you explore and randomly run across events happening in the world. When I play I generally see something interesting and run toward it, then sometimes get distracted by some crazy event happening. As an example I was in the Charr starting area yesterday and was at a camp with a couple charr and human NPCs. Suddenly harpies started flying into the camp and someone yelled "the harpies are coming! Don't let them steal our supplies!" I was the only player there, and I fought for a couple minutes, but ultimately the harpies stole all the supplies. Then the charr and human started talking to eachother. The charr told the human to go get the supplies back, she complained that she always has to do everything, he pointed out that he was the reason the charr aren't hostile toward her, and she agreed to go get the supplies. She ran off and I followed her, and when she got near the harpy nests she said "woah, that doesn't look safe. I'm just gonna wait here and someone else can help get the goods back." This started another event, where I killed harpies and collected the goods, and then brought them back to the human. Once she had enough, she ran back to town and told the charr she had gotten the supplies back.
I could have left at any time, all of this was optional. If I went back to that same camp right now, I might now see the same things happen. The harpies might not attack. They might attack and fail to steal the supplies.