This is in direct opposition to one of the three most defining aspects we were all taught about mammals: they have hair, they are warm blooded, and they do not lay eggs. To put this into perspective, whales, dolphins and even bats have enough respect for their mammal heritage to not lay eggs. And these crazy bastards spend their entire lives trying to be fish or birds. I mean come on, if mammals that spend their entire lives submerged in water can manage to give birth to live young, then the platypus has absolutely no excuse for this abomination of reproduction.