Answer:
As I went over London Bridge I met my sister Jenny; I broke her neck and drank her blood and left her standing empty.
I saw the dead bring forth the living. I saw the living bring forth the dead. What did I see?
An action done on mosquito bites
If you look, you cannot see me. And if you see me, you cannot see anything else. I can make anything you want happen, but later everything goes back to normal. What am I?
I'm a kind of cup that doesn't hold water, but makes a lot of noise repeatedly. What am I?
I am owned by Old McDonald.