The various Chandler pets over the years, in my opinion, are best described with two words: Parasite smorgasbord.
Not to anyone's surprise, the Chandlers themselves are more of a parasitic infection than the tapeworms, toxoplasmosis, and kidney worms likely living inside their pets.
Cats commonly carry toxoplasmosis, a parasite which increases your chances of being dumb and delusional after you infect yourself via contamination with cat feces. The longer it stays inside you, the more prone you are to be clumsy and careless, the more prone you are to believe stupid things possibly due to the decrease in intelligence; however, some people are resistant to the infection, while others are not. Chris may very well be the latter. This infection hypothesis, combined with his autism, may help us to better understand why he is who he is, and why he never improves.
Drugs like the one "Pharma Bro" Martin Shkreli raised the price of from $13 to $750 are used to suppress parasitic infections like toxo; however, a few antipsychotics, specifically Haldol, also suppress parasites, keeping people from entering even deeper states of delusion and helping them return to reality. Really makes you think...