This episode is another one of those stories where a miscommunication became a cause of serious trouble, but hey, action is more important than words, so it really didn't matter, as long as it's fun to watch, which it was, only at the second half of the show.
When Peg had a surprise coming her way, and went on her business deal, PJ and Pete had mistaked her for getting a new member of the family, thanks to Pistol's "spoilt child" ways. PJ failed to impressed his father with his hardworking houseworking, mainly because his father was quite busy, like most men are when they have a new "toy" to fix.
Pete and Goofy's attempts to prepare for the new baby had overshadowed Pistol and PJ in attention and care, that they decided to give Pete a baby that makes him wish that PJ and Pistol better than him. PJ played baby as lots of trouble were caused, and it worked, driving Pete nuts.