If they do, it could be because they want to feel more like part of the family, or it's just a particular animal's personality and that animal was matched with the person meant for it.
Ms. Rita Jean:
I have yet to locate the off switch on any Basenji and I've been around them since I was a baby. When you find it, you will let us all know, right?
If it's commercially made chocolate, they'd have to eat a lot to get sick. If it's 'real' chocolate, a little amount can be sufficient to really make them sick. Commercial chocolate is a lot of fake stuff.