Perhaps you don't remember ALF.
This extraterrestrial horror visited our planet in the late 1980s, first residing in the United States before fleeing to the security of German xeno-cultists. After a frenzied return to the states, the creature made a disturbing appearance on The O'Reilly Factor and was terminated by U.S. Forces in the Fox News green room.
Eater of Cats
One of the monster's more intriguing features was its dependence on cat meat. To be sure, the Melmacian consumed a variety of other foods as well, but it continually pursued feline flesh despite the moral objection of its human hosts. Why?
To answer this question, we have to consider feline meat itself. Despite moral concerns and the occasional rabies scare, cat meat is quite edible. In fact, a 2014 study found that humans enjoy cat bacon just as much as pig bacon.
ALF's alien physiology makes our quandary difficult, especially since the flamethrowers made such short work of his corpse. But here's a theory: Perhaps what ALF needed most from feline meat was the parasite Toxoplasma gondii.
If you'll remember, T. gondii is a parasitic protozoa found throughout the world. It infects more than half the world's human population. The organism can reproduce only inside a cat, but must travel through feline fecal matter, mice and birds before returning to the belly of the cat to breed. While the parasite causes no adverse effects in the definitive feline host, it boasts a slew of behavior-altering and potentially dangerous side effects in other organisms. We call such infections toxoplasmosis.
For us earthlings, toxoplasmosis can be transmitted through any infected meat, but ALF seemed dependent on the definitive host. He craved not the meat itself, but the possible parasitic contents. For some reason, only the highly-resistant oocyst stage would do.
Why? Well, consider the 2011 Cornell University study which found that T. gondii manipulates immune system cells at the molecular level.
Most warm-blooded immune systems fail to purge the intruders because the protozoa blocks immune cells from producing certain inflammation-stimulating proteins. T. gondii does this in order to maintain a balanced environment in the host, keeping it healthy while avoiding the ravages of its immune functions.
Perhaps ALF's seemingly mammalian body required such an infection to live on our world -- a sort of crude biohacking to stave off lethal tissue inflammation brought on by our hostile environment. And since it couldn't actively participate in T. gondii's life cycle, it was forced to continually feed on infected cats to maintain its toxoplasmosis.
The creature's erratic behavior might have been due in part to behavioral changes brought on by the disease.
Monster of the Week is a - you guessed it - regular look at the denizens is of our monster-haunted world. Sometimes we'll focus on the cultural aspects, but mostly we'll look at the possible science behind a creature of myth, movie or legend. Be sure to explore the Monster Gallery as well as the Monster Science video series.