Yesterday I was on the phone with a colleague from another offices; she needed me to do some spreadsheet analysis for her. I heard her say, "I've sorted the data by monotreme**." My first thought? "That's not a good system. There are only, what, two monotremes***?"

Actual first though should probably been more along the lines of, "What do monotremes have to do with sewers?"

*Probably you did not
**She was saying "Monitoring ID."
***Well, it turns out there are two families of monotremes, and while there is only one species of platypus, there are several species of echidnas.