My BIL had a rescue JR. She was most definitely a piece of work.
When she was about a year old, she jumped out of his car window (to chase a bike) while he was turning a corner and he ran her over. She broke her hip, had some surgery and she was fine except it made her lazy and eventually very, very fat (well, I also believe BIL overfeeds his dogs).
She was sooooo mean to other dogs. She had to be in charge all the time, always bossing everyone (people and dogs) around.