Il ne faut pas mélanger torchons et serviettes. Originally, this proverb has a strong social connotation: tea towels are for the poor and the servants, napkins for the bourgeois and the aristocrats. And one should never mix the two, socially, or otherwise.
When the wood pigeons migrate through SW France, some hunters become obsessed. It is sometimes called the 'Maladie bleue', or the blue sickness, due to the colour of the pigeons. This one has asked his wife to call his work to say that he won't be in for the next few days as he has the 'Maladie bleue'...