Good socialization I guess. IMO, I think any ball can become like that with good socialization. My pastel it extremely tame, you can do anything to him and he could care less. That includes "stroking him around the neck like he's a cat" haha He'll fall asleep on my chest and everything. My hatchling lesser, only 6 weeks old, was a month when I got her, extremely head shy to the max, and here I am, two weeks later and you could probably grab her head and pry her mouth open and she wouldn't mind. (not that I would do that, just making a point )