Yes, when they are very close to each other, ex. very good friends.

Thanks a lot, Joe!

Yes there are a few uses for that: -To give emphasis to a sentence, eg. Tι ήταν κι αυτό βρε παιδί μου! (My god, what just happened!) -To something absurd, you can say: Tι λες παιδί μου; (What are you talking about?). It's a bit rude. -Old people use it a lot for anyone younger than them. To be honest it's a bit obsolete, as a non-native I wouldn't bother with it =)