At one point in "Big Baby Scam", Old Man Hunger (the crazy, naked guy with the chicken drumstick on his head) takes a bath with Ren and Stimpy and starts whistling "In The Hall of the Mountain King." This is the Leitmotif of Peter Lorre's character in the movie M — a pedophilic serial killer.
Fridge Brilliance: That scene is one of many to be edited in reruns on television. Maybe someone in the S&P department discovered this or already knew it in some capacity.
Stimpy frequently touts the edibility of Gritty Kitty litter (he and Ren even consume it on-camera). In real life, cats do eat litter, but only if they're ill or suffering from a vitamin deficiency.
In "Ren's Toothache", Ren is shown to have rotten, stinking teeth. In real life, chihuahuas frequently have dental health issues, and those problems can drastically shorten a chihuahua's life, or even kill it.
"Space Madness". At first glance, it doesn't seem too bad, but when you really think about the scenario: Ren and Stimpy are both astronauts who haven't seen Earth in (presumably) years, who are the only ones on their ship, who don't eat real food (instead, they eat pills), and who have six years of free time on a ship where they have nothing to do but stare at each other. Is it really any wonder why Ren snapped?
Sven Hoek is introduced as Ren's cousin. However, Ren remarks that they were littermates and shares a photo of the two as newborn puppies. If they were littermates, they were born of the same mother, but as cousins, their parents were siblings. In other words, Ren and Sven were the product of brother-sister incest.
When Ren threatens to torture and beat up Stimpy and Sven for making him angry it makes you wonder if Ren threatening to take his abuse further than beating up Stimpy has happened in the past.
To be exact, Ren becomes angry for Stimpy and Sven ruining his most prized possessions. One of these things is a collection of rare, incurable diseases in jars. Jars that have been opened. Letting the diseases out.
In a more subdued bit of fridge horror, one of Stimpy's letters reads "My boyfriend is mean to me- my only friends are you and my TV." That is plenty disturbing in and of itself.
In the Adult Party Cartoon episode, "Ren Seeks Help," Ren seeks psychological help after abusing Stimpy in some (unexplained) manner that is regarded as being horrible, even by Ren himself. He goes to Mr. Horse and proceeds to tell him about his youth, and the various displays of genuine psychopathy he exhibited then. He finally works up the nerve to tell Mr. Horse what it was he did to Stimpy, and then asks, "What do you think is wrong with me?" After some consideration, Mr. Horse says "So you wanna know what's wrong with you? You really wanna know?" He then punches Ren in the face and screams "YOU'RE FUCKING CRAZY!!! THAT'S WHAT'S WRONG WITH YOU!!" When you consider his sexual relationship with Stimpy in Adult Party Cartoon and the various abuse he dishes out one can't help but wonder what he actually did to Stimpy to make him so upset. In this case, rape or torture can't be ruled out.
At the end of "Nurse Stimpy," Stimpy catches Ren's illness, possibly even worse than Ren did initially. It's likely that he came down with it due to a combination of stress and a lack of sleep- not getting enough sleep tends to make your immune system shut down.