These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternative Character Interpretation: There's a fan theory that states that the events in the show are just normal events as seen from a dog's perspective. Some specifics of the theory include:
Courage actually lives on a regular farm. He just thinks it's in "the middle of nowhere" because his owners are too old to walk him and he doesn't know what's outside.
The "monsters" in the show are just normal people or objects that Courage imagines as something completely different. That would explain why Eustace and Muriel rarely seem to notice any of them. Courage is actually freaking out over a postman, or a vacuum cleaner.
A dragon coming out of absolutely nowhere (pun not intended) and eating Eustace in the last five seconds of the episode.
Eustace getting mauled by a Siberian Tiger while deer hunting.
Seems as though animals are always coming out of nowhere to attack Eustace, as he got attacked by a giant squirrel in "Family Business".
Most of Courage's nightmares from the last episode could count, especially that blue thing. It really had no importance to the rest of the episode except to scare you straight and it really wasn't seen or mentioned again in those other nightmares.
When Eustace gets cursed by Shirley the Medium to always have a black cloud following him, at one point he passes a man poking his head out of an alleyway. The man is being strangled by a green tentacle and hurriedly asks Eustace if he will deliver a message to his fiance that he won't be able to make the wedding. Eustace completely ignores him and the man is whisked down the alley by...whatever that was. It has nothing to do with the plot other than to show that Eustace is still a selfish asshole.
The way Katz gets defeated in "Katz Under the Sea".
"Snowman's Revenge" has Snowman breaking out into a So Bad, It's Good musical number about... a chilly love story? Huh?
"Courage Meets The Mummy" opens with an archeologist dusting off a gem inside the Mayan temple, which then shoots out a beam of light which gets reflected off some things and causes a disco ball to come out of the ceiling while some music plays for a brief moment. Afterwards, the archeologist just shrugs it off and continues dusting off the gem stone.
Cargo Ship: In "The Gods Must Be Goosey", the Goose and Eustace's Truck are getting married at the end of the episode.
Complete Monster: Katz. Since the show has Negative Continuity, his motives tend to change, but what he does is always inexcusable. In his first appearance, he ran a Hell Hotel where he fed all his guests to spiders, taking sadistic delight in doing so. In a later episode, he ran a health spa where he transformed his guests into machines and forced them to fight for his own amusement. In both of these appearances, he didn't seem to get much gain for these action, but did them all with a Slasher Smile on his face. In short, he's an Ax-CrazySerial Killer played straight...on a kid's show! What makes Katz even worse is the fact that the family is heavily implied to just be the latest in a long line of victims to fall into his clutches.
Hell Is That Noise: Courage's "YEEEAAAAAHHHHHHHHHHH!!" scream from the Cartoon Network game "Pharaoh Phobia". Unfortunately, unless you turn the sound off on your computer, you will be hearing it many, many, many times before the game is over.
The repeating "It's Doc Gerbil's World!" song that sounds like the demented cosmetics themed version of "It's A Small World After All" during the boat road in "Human Habitrail".
The "Freaky Fred" episode. The most disturbing scene is when Fred and Courage are locked in the bathroom together and Fred shaves Courage with a manic grin on his face while a haunting chorus of "la-las" starts to accompany the already eerie music.
"RETUUURN THE SLAAAB!"
"You're not perfect..."
Genius Bonus: The difference between the words "bravery" and "courage" is that a brave man isn't afraid to start with, while the courageous man is afraid but does what has to be done in spite of his fear. That's Courage the Cowardly Dog in a nutshell. And it's why he's awesome.
The idea of on of the Valkyries falling in love with the incredibly disgusting Troll king, and soon the other Valkyries and the trolls falling in love is just, gross. Don't think about their Honeymoon to much...
That scene doubles as a Crowning Moment of Funny because the as the Valkyrie and Troll King were singing about how much they love each other, they would not. Stop. Singing, Despite the fact that the rest of the Valkyries and Trolls were on their way to the cave. Added bonuses include going to the scene of the Valkyries and Trolls running their way over there, and cutting back to the Valkyrie and Troll King, STILL SINGING, and cutting back over and over, but also Courage Lampshading it.
The Demon Head in "Courage In the Big Stinkin' City".
King Ramses' in "King Ramses' Curse".
What Do You Mean, It's for Kids?: A lot of people probably think Courage is for an adult audience with all the strange horror and black comedy. One extreme example of this is the episode called "The Mask", which is basically a cross between a psychological thriller and a gangland drama (with implications of a lesbian relationship).