Livescience.com reports that
"Even eating just a couple of leaves or licking a few pollen grains off their fur can cause cats to suffer acute kidney failure, she said. All parts of these plants, which are members of the Lilium and Hemerocallis genera, are considered poisonous. ... The first symptom of lily toxicity in cats is vomiting... Over the next 12 to 24 hours, the cat may start to urinate frequently, but then urinating might stop altogether, which is a sign of kidney failure. If not brought to a veterinarian, the cat will die within four to seven days. Other signs to watch for include drooling, loss of appetite and decreased activity." ... Read the rest @ http://www.livescience.com/44829-lilies-kill-cats.html
Other Easter-time risk for pets include "Easter grass" and chocolate.