Pettings
After Angelus killed her pet fish, Willow doesn't want them any more. She's not sure she wants any pets, really. They seem even more vulnerable than people. At least her parents aren't likely to invite a vampire into their home, but let little Spot or Fluffy get outside without someone paying attention, and that could be the end of that pet, too. If not the demons of Sunnydale, well, there were coyotes and raccoons in Sunnydale, they were just lesser predators on the Sunnydale food chain.
So Tara's kitten, Miss Kitty Fantastico, came as a surprise - none of them had had any pets since the whole 'lose the soul' thing, and even before then, the closest Willow had to a pet was a Beagle Xander's dad brought home. Snoopy stayed with the Harris family for about a month before the neighbors' complaints of Snoopy's howling sent him away. Xander had cried for days afterward and Willow still didn't know what happened to Snoopy.
But Miss Kitty was such an engaging ball of fluff, curiosity, and cuteness all rolled into an adorable kitty package, Willow quite lost her heart.