The female species. Seemingly completely incapable of packing sensibly and more importantly, packing in accordance with available space and duration of the trip. Without fail, with every packing opportunity, my dear wife will haul out the biggest bag available and stuff it to the seams, pausing only to inquire whether or not I still have space in my bag for say her hairdryer.
Or twenty million towels.
Either way, getting the car ready for the trip involves quite a lot of inventive reshuffling and an exercise in packing logistics.
I’m beginning to think that the airports have got this one right by restricting the amount of stuff you can throw aboard! :)