There is a certain logic to this joke. On the Church calendar it is Presentation Day, when Jesus is presented in the Temple. It is the last of the Nativity stories.
Actually, more than 100 years ago farm wives did exactly what Agnes is doing, carried eggs around in a vest like contraption to keep them warm so they would hatch. It was called a “hatching jacket.”
There is a certain logic to this joke. On the Church calendar it is Presentation Day, when Jesus is presented in the Temple. It is the last of the Nativity stories.