Negative Continuity: A number of episodes end with Courage losing or the characters dying, yet they're back to Square One the next week. Even the original short film featured Eustace turning into a monstrous alien chicken and then getting vaporized. None the less, there's still a few reoccurring villains in the roster providing continuity in spite of it all.
Nightmare Face: The violin girl in "Courage in the Big Stinkin' City".
No Celebrities Were Harmed: Snowman had Sean Connery's speech pattern so downpat, that some fans thought Sean Connery actually did his voice (but it was, indeed, Paul Schoeffler).
In the episode "House Calls", the Bagges' new neighbor, Dr. Von Orbison, is almost a dead ringer for Roy Orbison.
No Sell: There's Eustace's immunity to Dr. Zalost's unhappy cannonballs because he's immune to emotions. He was also unaffected by the Cruelty Curtain (because he's already a jerk), as well as Muriel (due to her Incorruptible Pure Pureness) and Courage (due to Muriel's fabric softener).
Nothing Is Scarier: The ending to the Le Quack episodes ends with the titular villain escaping from his confinement and he always leaves behind evidence as he goes such as a police van crashing with no officers in sight, and a prison on fire with no signs of other convicts, though it's never explained how he managed to escape every time. Since he usually fights Courage through the means of cartoonish antics, this just makes the endings even scarier.
"You see that door? You wanna know what's behind that door? You don't wanna know what's behind that door. See those bones? Wanna know what made those bones? You don't wanna know what made those bones."
Eustace getting the bad end of the deal and suffers a fate.
One-Woman Wail: "Doc Gerbil's World", where the final boat chase between Doc Gerbil and Courage is accompanied by almost no sound other than this. It simultaneously comes off as Soundtrack Dissonance and Crowning Music of Awesome. The only reason it's Dissonance is because said chase scene was between a plaid-wearing gerbil and a pink dog on jet-skis.
In the early episode "The Shadow of Courage", whenever Muriel would catch Eustace abusing Courage in any way, she would run at him with her rolling pin, accompanied by a triumphant, operatic one-woman wail.
Opaque Lenses: Muriel & Eustace, as well as Eustace's whole family. Similarly, all of the recurring normal, non-villainous human characters except the General had their eyes obscured. This seems to emphasize Courage's status as a Cassandra type, as nobody else sees what's obvious to him. Subverted in the Hothead episode (though it's fairly surreal looking).
Pass Fail: Kitty's mask and dress are a fairly obvious metaphor.
Pet the Dog: Horribly, horribly subverted, in "The Precious, Wonderful, Adorable, Lovable Duckling", where a duckling thinks Eustace is its mommy. Eustace tries to be a good mom, but the bird secretly wants to kill Muriel. Eustace doesn't seem to care about Muriel (then again, did he ever?), even if the bird blatantly tries to kill her. It doesn't help the bird is probably as bad as Eustace.
This ended up with the pair being blown to the moon (in Muriel's place), and each pairing lives quite contentedly.
Eustace also has a few more genuine moments of this. For example, in "The Mask", he seems genuinely concerned about Kitty's past, and reassures Muriel when she worries about her faults.
Physical God: The Goose God and an unnamed, female, teenage storm deity.
Police Are Useless: Pretty much 90% of the time. For example, at the end of every Le Quack episode the police come to cart Le Quack off to prison. He always escapes.
Public Domain Soundtrack: Most episodes (certainly not all, but most) will feature a classical piece, either as a random part of the episode's soundtrack, or even as a character's Leitmotif.
Recycled Premise: Season 3's "Curtain of Cruelty" has a similar plot to Season 2's "The Tower of Dr. Zalost", with anger and hostility infecting the Nowhere townspeople instead of sadness and depression.
Rule of Funny: Determines whether Courage can speak or not in each episode.
Rummage Fail: Whenever he'd look through his impossibly large, nonexistent "pockets", he'd normally have to pull out three or more objects until he got what he needed, at which point he'd stuff it all back in.
Sand Is Water: One episode has the titular character forced by Eustace's mother to hunt a sand whale, who is trying to get his accordion back from Eustace's mother. And Courage is forced to row a boat in the sand. Another slight subversion, considering that the ground only worked like water for the sand whale, and not the rowboat.
Scare Chord: HMMM. I believe that all of the Title Cards had one of these playing in the background. Especially Perfect and Wrath of the Librarian.
Whenever Katz made an appearance. You could tell a few seconds before he was actually shown, by the creepy beat that suddenly started playing. And it kept playing. Until it could cause shuddering years later.
Scenery Porn: A lot of the shots of the farm house either at night or at sundown are awfully pretty for a Crapsack World. The show uses a technique of overlaying photos with animation, so the skies you see are (mostly) pictures, although exaggerated or altered.
Schmuck Bait: Courage's computer enjoys baiting him with false advice that results in him being tarred and feathered among other things.
Second Person Attack: In "1000 Years of Courage". Courage picks up a banana, attempting to eat it, but it turns out to be a living baby creature. Courage makes a dash for it as its mother hits him over the head twice with her purse.
Strong Family Resemblance: Eustace is a carbon copy of his parents. Lampshaded in "The Sand Whale Strikes", when the Sand Whale has confused Eustace for his father, Ickett. Eustace pulls out a picture of his father (who looks exactly like him with a huge beard) and says "I don't see the resemblance."
Stylistic Suck: The flashbacks in "Remembrance of Courage Past" have choppy animation.
Super Strength: Eustace is amazingly able to eat just about anything with no problem, despite having no teeth whatsoever - this includes lobsters still in their shells, raw carrots, candy canes, and other hard/crunchy foodstuff.
Surreal Horror: Especially with the blue fetus thing in Courage's dream in the grand finale, a perfect example of Uncanny Valley involving computer animation, and the Synchro-Vox tree and moon qualify as well.
Suddenly Voiced: The tiger from "Squatting Tiger Hidden Dog". Also Courage, as a recurring character trait.
Synchro-Vox: The Spirit Of The Harvest Moon and The Magic Tree Of Nowhere use this technique.
Talking Animal: And boy are there a lot of them! Strangely, Courage talked frequently in the early episodes, but later became a Speech-Impaired Animal over time. This is actually a result of Executive Meddling, CN forced Dilworth to give Courage less talking lines as they felt he was funnier as a babbling animal. The latter is somewhat subverted at one point. Realizing he can't talk to Muriel directly, he runs to a payphone and calls her.
Vocal Evolution: Eustace's voice has become noticeably deeper halfway through Season 3. This was due to his original voice actor Lionel Wilson retiring due to ill health, and was replaced by Arthur Anderson for the rest of the series.
Voice Actor: Averted. With the exception of Lionel Wilson, and Season 1 featuring Jim Cummings (Fusilli) and Kath Soucie (Little Muriel), most of the voices on this show were performed by local New York City-based stage actors, or Stretch Films employees.
Why Don't Ya Just Shoot Him?: Katz frequently plays this straight with bizarre death-traps that would kill Courage indirectly, although, when the cards are down, he often subverts this by attempting to strangle the dog with his bare paws.
In "Big Ball of Revenge", the littlest toe points out how silly this would be, and gets a Dope Slap for his trouble.
Why Do You Keep Changing Jobs?: The recurring red mustache guy holds many different jobs depending on the episode. Many of his jobs include working as a Nowhere police officer, an archaeologist, a captain, a pilot, a New York police officer, a ranger, a general, a pirate, and a mayor.
Wild Take: Courage's tendency to scream in terror actually saved him in a later episode when he screams so loudly for so long that he shatters the foundation of his house, sending a team of series villains plunging into a bottomless pit.