So many baby bunnies end up being abandoned after they turn into rowdy "teenagers". The House Rabbit Society and other rescue organizations do great work saving bunnies...but it's better to remember that they are not toys for kids.
A couple of summers ago I found about 8 or 9 critters scattered around my lawn early in the morning. At first I thought they were rats but it seems that my dog might have grabbed a female possum during the night and shook the babies off her. Mom possum disappeared and we are lucky enough to have a wildlife rescue about 20 miles away and they told me to bring them in. Baby possums can't produce enough body heat at their naked stage so bundling them up is not enough. You have to give them suplemental heat even in the summer.