Nature programmes frequently throw something at viewers to remind them that life is nasty, brutish and short. In amongst the parental penguins, fluffy ducklings and playful sea mammals there's a universe of terrors.
Parasites are the worst. The fungi that make ants' heads explode, the larvae that eat caterpillars and spiders from the inside out and the tapeworms that turn snails' heads in bulging, pulsing beacons to attracts birds and start the whole process off again.
Yes, the parasites are the worst. Sure there are things that will bite your head off or drain your blood, but that idea of parasitisation, infestation - to have something else living in or on your body, slowly consuming you - is as hideous as it gets.
Which is why I'm revolted by EDF Energy's new advert, which features a dog at an advanced stage of parasitisation by some amorphous blob with eyes. This particular parasite (it's called Zingy - just image that: "I'm afraid you have a Zingy living in your eyeball") sits on the back of a dog, where it can't be reached, free to drain the life force from its unfortunate host.
Cruel hooks dig into dog's skin and ensure that it can't be removed without taking a huge chunk of the canine's back with it. Meanwhile long ganglia reach into the mutt's brain stem, controlling its every move.
Eventually the EDF parasite grows so fat on the blood and nutrients that the dog is left a dry, lifeless husk. Squirming hideously it makes its way back home - to EDF Energy headquarters in London - there to be enveloped into the collective. No-one has lived to see it and tell the tale, but it's believed to resemble a giant farting brain with the face of John Selwyn-Gummer.
By a happy coincidence, EDF Energy was recently discovered to have incentivised its salespeople to sell the unwitting Great British public the most expensive energy tariffs possible.
EDF employees have told The Argus how, despite knowing the customers could be getting a better deal on other tariffs, they were told not to mention cheaper deals unless specifically asked for.
Pfft. Parasites eh?