Well, what do you expect from a show where the main characters are Born Unlucky and are abused by nearly everyone in the town where they live? A happy show? Well, there are some moments that tug at the heartsrings rather than tickle the funny bone.
- The parents' flashback in The Great Parent Mystery, where the baby CatDog are separated from them in the vortex.
- The scene at the beginning where CatDog are standing outside the Parents' Day celebration and can't go in because they don't have parents to celebrate with. To make things worse, Cliff shows up with his parents to the festival and makes fun of the twins for not having any parents.
- Also the scene where Dog comes this close to just giving up on looking for their parents entirely. Seeing Dog, the one who was most optimistic about them finding their parents, sounding utterly broken as he says that looking for them was a "dumb idea," and that all of his theories of what happened to them were "stupid," is just heartbreaking.
- Also "Sneezie Dog," where they have to build a brick wall between each other due to Dog apparently being allergic to Cat. Thankfully, he isn't.
- Cliff, Leader of the Greaser Dogs, learning the hard way what it's like to be exactly the kind of outcast that he picks on CatDog (mostly Cat) for being when he winds up with Eddie temporarily attached to him in "Squirrel Dog." Not only is he kicked out of the Greasers due to him and Eddie now being a "two-headed freak" in the eyes of Lube and Shriek (One of the rules for the gang literally reads "Greasers are not two-headed freaks"), he can't go anywhere without someone in town calling him a freak, eventually winding up sleeping in the rain in a cardboard box.
- The worst part is the inevitable use of Status Quo Is God: during the episode, CatDog were the only ones to show Cliff any compassion and kindness, taking him in even after all he's done to them and despite the fact he's Cliff (he comes to them and begs for help asking them to "teach him your freakish ways"). So, once he finds out he just had Eddie the Squirrel glued to his jacket, does he decide to stop bullying them? Nope! It's back to the same abuse.
- Similar is "Dog's Strange Condition," the episode where Cat exploits the pecan tree growing out of Dog's head (the result of an allergic reaction), only for the tables to turn on him at the end when Dog recovers, but Cat inherits the symptoms... just as Dog is about to debut in a freak show! Feeling the exact same humiliation he put his brother through, Cat looks around awkwardly before clearly welling up.
- Dog's song about wanting a home in "It's a Wonderful Half-Life."
- The episode "CatDog Doesn't Live Here Anymore" has Winslow and the Greasers feeling guilty about mistreating Cat and Dog when they think the two moved away. They even sing a sad version of the show's theme song at one point. However, at the end of the episode, it's revealed that Cat and Dog were just on vacation.
- This part is particularly hard hitting:
Cliff: (laughing) Yeah, we don't have CatDog to kick around anymore! (everyone slowly stops laughing as they realize what he just said)
Shriek: (picks up a picture of Dog and starts to tear up) Those... days are gone... goodnight (starts crying) sweet pup! - Lube lamenting his loneliness in "Lube in Love." It has a happy ending, though.Lube: A wise man once said, "I am what I am." And I am...
Cat: A mechanic?
Dog: A Greaser?
Lube: ...alone. - The episode where Shriek is revealed to be rich will probably make you feel bad for Cliff of all people, when due to a misunderstanding he ends up thinking that Shriek doesn't want to be friends with him or Lube anymore. Heck, even Cat's "The Reason You Suck" Speech in response comes off as extremely cruel in that regard. Becomes heartwarming when the Greasers get back together in the end, though.
- The episode Back To School has Cat realize that he never finished his last day of school, thus never technically graduated. He can't remember why he didn't finish the last day, until a single day of going back and being relentlessly bullied brings his repressed memories back. He bursts into tears, chanting "Cat is a loser" along with the bullies.
- Pretty much any time Dog gets hit with Break the Cutie or falls into some sort of slump. Episodes like Fistful Of Mail or Dog The Mighty where he gets bullied by delivery men (such as a mailman, a paperboy and a girl scout) in the former and laughed at by the entire town of Nearburg in the latter are pretty good examples of this.
- It's a blink-and-you'll-miss-it moment, but there's the look on Cat's face when the mailman bullies Dog by shoving his mail in his mouth in "Fistful of Mail."
- In the first episode, "Dog Gone," Cat decides that he wants to be alone, away from Dog. However, he soon realizes how lonely he is, and eventually he winds up in tears and tells Dog he misses him.
- While this is a Sadist Show, "The Unnatural" is a particularly cruel example. First, everyone makes fun of Cat and calls him a "loser," and he feels so bad that he cries about it for an entire day. Then, he tries working hard to improve at baseball, but it doesn't work, so Murray the Mule shows up and tells him he can do it if he "believes in himself." Cat ultimately fails, and Murray also calls him a loser and leaves. The end of the episode shows that even a mailbox is better than Cat at baseball.
- The scene from Climb Every CatDog where Cat breaks down in tears and calls himself a loser.
- The ending of Spaced Out, which crosses into Dude, Not Funny! territory. Cat and Dog get trapped inside a scifi movie, and Cat is forcibly grabbed and kissed by a grotesque alien monster again and again, several shows a day. Cat screams for help and ends the episode in tears, but Rancid (the movie theater owner) forces him to endure it because the audience loves it. Crosses into Nightmare Fuel.
- In "New Leash on Life," Cat lies to Dog that there's a new leash law in Nearburg and dogs who don’t behave well will get sent to the pound. Dog has an Imagine Spot where Cat callously abandons him at the pound and gets a better dog.
- In "War of the CatDog," CatDog's family finally shows up for their family reunion for the first time ever, but since Cat and Dog just destroyed the house, they think they got the location wrong and leave.
- At the end of "Curiosity Almost Killed the Cat," Cat confesses to Dog that he read his secret diary. Dog is almost heartbroken by the revelation, and Cat ends up in tears.Dog: Cat... how could you?
