Each time I got a foster, they were always a bit withdrawn and some just followed me around. It takes them a few days (some even weeks or months, depending on the trauma they have endured in their lives) to size things up, getting to know the new people & other pets and when they finally realize they re safe and loved, then they just open up like a rose. It's only then that you get to see who "they" are too. Their real personality starts showing up.