Fainting goat kittens.

These kittens have Congenital myotonia. Wikipedia defines it as:

Congenital myotonia is a genetic, neuromuscular channelopathy that affects skeletal muscles. It is congenital, meaning that it is present from birth. Amongst other problems, it causes delayed relaxation of the muscles and rigidity. Symptoms include delayed relaxation of the muscles after voluntary contraction, and may also include stiffness, hypertrophy , sluggishness of the muscles, transient weakness in some mutations, pain, and cramping. The disorder is caused by a genetic mutation involving the chloride channel of the muscles.

So sad but still kinda funny.