LET'S JUST ALL START SPAMMING !!! Hahaha, sorry.
Anyway, the two most memorable characters are the ones that get their own short stories within the story, and those are the characters in the back of the book. We'll get to them in a bit.
One of them is called Jack and the Girl Who Was Never Born, I think. This one was really the only girl that survived, and she has a little brother as well. There is lots of time-travel and time travel nonsense in this book, and I didn't even realize at first that it was a book about time travel...although the title says it all. It seems that he was born when there was a time travel portal in the moon and a girl appeared and said she would give you one thing if you would just go back and save her. He went back and saved her, but the time portal started to move again and she got killed.