Munchhausen by Proxy Syndrome is when a mother or father harms their own child in order to obtain attention/ sympathy for themselves. (Like the little girl in the Sixth Sense who's mother feeds her soup with Lysol in it.)
Capgras'syndrome is the delusion that a loved one has been abducted and replaced by an exact duplicate, by (chose one) CIA, Russians, aliens, neighbors.For other mental oddities, you might want to read something by Oliver Sacks.