my kitten Bootsy wouldnt do just about anything the first few days we had her. she wouldnt eat, sleep, drink, pee, poop, anything. eventually though, she got used to her surroundings and is now very active and very vicious.
though in this pic, she doesnt look it:
this is her the day we got her, a month ago almost. she looks chubbier in the newer pic above, but thats just cause shes squnched up. shes definitely gotten bigger though.