Gus was humping the day I got him (eight weeks). I couldn't believe it. At first it was his stuffed animals but a few times he tried my arm too. For some reason it was when I was sitting with my arm bent. He likes elbows.
He also started to lift his leg at 10 weeks. Not completely just an inch or so off the ground. He recently has started to show pink -eek. I am really hoping this will stop when he is neutered next month. It really freaks the kids out.