While people might remember it fondly, in reality, CatDog was a creepy show. It was one of the most bizarre '90s cartoons ever created and considering the existence of Rocko's Modern Life, that's saying something. Some of the reasons that CatDog was super weird are inherent in the concept - a cat and a dog attached at the stomach is unnatural even before you start thinking about the implications. Those implications are pretty terrifying, though. For example, how do the siblings go to the bathroom? No one knows for sure but there's no possible explanation that isn't horrific.
When re-watching any old episodes from this show, further weird details emerge. Another odd fact, Cat and Dog's sarcastic roommate, Winslow, actually raised them from childhood. If that doesn't sound strange, then you're not remembering all the episodes when Winslow and Cat actively tried to murder each other. Oh, and there's also an episode when Dog hallucinates that raw meat is talking to him. He ends up trying to cook and eat Cat. You probably won't find that episode in any Nickelodeon fan art.
There's No Obvious Way For Them To Use The Bathroom
One of the biggest CatDog mysteries is how they go to the bathroom. People have come up with plenty of theories and all of them are terrible. One involves excreting waste through each other's mouths in a reverse centipede sort of situation. One involves their excrement being teleported to another dimension and one involves having separate anuses and most likely, separate penises as well.
Creator of the characters Peter Hannan says about their situation:
"No one knows [how they relieve themselves], myself included. What I used to say, because I was worried that kids might think CatDog would explode if they didn't go to the bathroom, was that they definitely do go to the bathroom, but no one knows how. Nobody ever asks how Mickey Mouse goes to the bathroom, so we don't really need to know."
Mickey Mouse presumably has the parts required for the process, though. We don't see them because he's wearing pants. He doesn't have another animal's head attached to his rear end. So it's probably a different sort of situation.
They Spend An Alarming Amount Of Time Inside Each Other's Mouths
Cat and Dog spend a disturbing amount of time just hanging out inside each other's mouths. In one iconic clip, Winslow walks in on the two of them standing in their room while Cat is rooting around inside Dog's mouth. In another much more terrifying scene, Cat crawls through their body, leaves his skin behind, and comes out through Dog's mouth as a horrifying skinless monster.
He does this in order to forcibly brush Dog's teeth.
Winslow Is Like Their Surrogate Dad But Their Relationship Is Terrible
Many CatDog viewers may have forgotten that the sarcastic little mouse who lives with them is basically their father. Yes, Winslow found Cat and Dog when they were babies and raised them to adulthood. Despite his parental status, Cat and Dog have shockingly little respect for him; they treat him like an irritating roommate, not like a dad.
It's worse than just petty bickering, however. Cat has tried to kill Winslow on multiple occasions and Winslow constantly blackmails and harasses both Cat and Dog. He also plots to kill Cat at one point. Theirs is a strange father-son relationship.
Cat And Dog Have Zero Respect For Each Other
One of the creepiest things about CatDog is how little the brothers seem to care about how their actions affect the other. They'll knowingly chow down on food that makes the other one sick. When they find out that Dog's snacking affects Cat's teeth and vice versa, they intentionally try to wreck each other's teeth out of spite. When Dog is initiated into the Greasers he lets Cats be tortured until finally deciding to abandon the group.
If Dog runs, Cat usually gets injured. If Cat comes up with a scheme, Dog usually gets manipulated into doing something humiliating. They rarely compromise with each other about how to use their shared body and they rarely demonstrate affection.