Hi. I recently done the "Help Rood Raise a New Pet!" quest. It's a cash quest in which You have to kill mobs near Heine. I heard that if You kill a large number of them and bring quest items to NPC he will give you a Pet.
This was a big question when this quest was originally implemented due to the wording.
Final word was that NO it is not possible to get a Leinruk pet nor was it ever intended that you get one. (It was just background text on why you were collecting the eggs for the NPC.) I think Hellrose was the one to translate some Korean question about this quest, but this was so long ago now, that the whole response and its origins is a bit hazy. (Might have just been a NCNA question that actually got answered by the NCKr team in the distant past even.)