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.
Anticlimax Boss: Used and Played for Laughs in "Robin Hoek"; before Robin rescues Maid Moron, he has to fight The Sheriff of Dodge City (George Liquor) who he defeats by whipping out a turkey baster and smothering him in a shot of gravy. Liquor immediately collapses and surrenders Maid Moron.
Archive Panic: The original show ran for five seasons and 94 episodes (100 if you count Adult Party Cartoon), and including the bumpers, it would take almost 23 hours, or about an entire day without sleep, to watch the entire series.
The eclectic selection of stock sound cues have some very memorable tracks of music, particularly cues like Beethoven's "Pastoral Symphony" and "Clair De Lune", among other obscure pieces of classical music.
No wonder, since this is the melody of "God Save The Queen".
In the German dub it's absolutely beautiful. Especially when Ren harmonizes with Stimpy.
Bizarro Episode: The series is very offbeat to begin with, but even then some episodes stick out like a sore thumb, such as "Haunted House" (which was an unmade Tiny Toons episode that Spumco was supposed to have a hand in, but ended up making for themselves).
Broken Base: "Ren Seeks Help." It's either the strongest episode in the series, or its most ghastly; the point of contention lies within its scenes of graphic animal cruelty.
Creator's Pet: George Liquor. Many people (both in-universe and in real life) dislike him, but John Kricfalusi, somehow, is really fond of him (possibly due to him being the only Ren and Stimpy character he still owns).
A more nuanced example, since the character actually only appeared in a couple of episodes of the series, largely due to Nickelodeon's hatred of the character and thus having no problem handing Kricfalusi the rights to him when he left the series. He has a potential future however, with Kricfalusi himself as The Other Darrin.
Ear Worm: Many of the stock sound cues, including classics like "Pizzacato Playtime", "Screw on the Loose" and "Folli the Foal".
The Muddy Mudskipper TV show theme.
The LOG song.
The "Loop of Death" music from Adult Party Cartoon, which is a recording of the classic jazz song "Hold That Tiger".
Esoteric Happy Ending: Ren and Stimpy's tearful reunion in "The Big Shot" is cut short by Ren slapping Stimpy for giving away his 47 million dollar fortune.
In "Rubber Nipple Salesmen", Ren and Stimpy succeed in selling their rubber nipples to a suburbanite couple... who then kick Ren and Stimpy onto the backs of a couple of crazed bulls that they ride into the distance.
"Powdered Toast Man" ends with PDM becoming president after saving the Pope; in office, he promptly burns the Constitution to start a fireplace (which was edited on American TV after it first aired) as he spends time with his lovely assistant.
"Man's Best Friend". By thrashing George Liquor half to death with an oar, Ren earns his approval and praise for being such a good guard dog. Ren and Stimpy are then rewarded with doggie treats, and the three of them dance happily to an upbeat Raymond Scott song. (The aforementioned thrashing was one of the things that pissed off Nickelodeon and led to them firing John later.)
Fanon Discontinuity: The Games Animation episodes and the Adult Party Cartoon episodes might as well have not existed in the eyes of fans.
The romantic tension between Powdered Toast Man (whose secret identity is that of a clergyman) and his Catholic schoolgirl assistant. After the Catholic clergy sex abuse scandals of the 2000s, this comes off as really unsettling (though the only good thing you can take from this is, "At least the lovely assistant wasn't a boy. Then it would have been unwatchably awkward.")
Freud Was Right: All over the series in regards to Ren And Stimpy's relationship. And as mentioned above, the implied romantic tension between PTM and his assistant in "Powdered Toast Man", especially the ending shot where they start a fire and roast a weenie and marshmallow over it.
Genius Bonus / Truth in Television: In "Fire Dogs", Stimpy puts out the building fire with kitty litter; in real life, Kitty Litter is usually inflammable, since it's often made out of ground up clay.
Growing the Beard: The show definitely got off to a good start, but the second season is universally considered a significant improvement over season 1's helter-skelter quality, and by many to be the series peak; Ren and Stimpy's personalities and voice work are more fleshed out, the drawings, animation quality and background art are much better (especially the episodes animated by Carbunkle) and the cartoons became much better in story structure, humor and pacing. Even the heavily contested Adult Party continued raising the bar higher; it had some of the most ambitious animation ever made in a western made-for-tv cartoon— the drawings and animation blow anything from the original series out of the water, the background art shirted from heavy stylization to a more naturalistic look and more in line with the painters personal styles , and the tone, characterization and acting (especially in episodes like "Ren Seeks Help") go further than even the standard set by the season 2 episodes.
Hilarious in Hindsight: In "The Big Shot!", one of Stimpy's lines in the Muddy Mudskipper cartoon, "I'm huntin' for a wabbit!" and "Blow me down!" Years later, Billy West (Stimpy's voice actor) was hired to play Elmer Fudd on The Looney Tunes Show, and also briefly played the role of Popeye in the 2004 made-for tv special.
"HAPPY HAPPY, JOY JOY!" note Stimpy's recurring catchphrase, as well as the famous song number from "Stimpy's Invention".
Ren's infamous catchphrase "You eediot!"
The "Ren Snaps" sequence from "Stimpy's Fan Club", where Ren imagines himself as President, pressing "The Button" which atomizes Australia, has become a popular meme on YouTube called "You Dare Not Agree With X", where a picture of X character is photoshopped over Ren.
Seasonal Rot: The Games episodes. The Adult Party Cartoon episodes tried to turn things around, but, alas, those episodes made the Games ones look like the Spumco ones.
Seinfeld Is Unfunny: The show was Nickelodeon's first big breadwinner and hugely popular in its prime, and many of the shows elements, particularly it's humor and drawing style, were shocking and unprecedented when it first hit the air. As a result, it ended up becoming one of the most ripped off cartoons of all time, to TV cartoons what Snow White is to animated features and what Mario Kart is to racing games. Nearly everything the show pioneered that was considered unique and groundbreaking when it first appeared have since been so heavily imitated that they're now considered ubiquitous elements of contemporary cartoons—much to John K's chagrin, since he felt that those cartoons only copied the many, many mistakes he made on the show, instead of what he felt he did right. Though, unlike most cases of Seinfeld Is Unfunny, this show is still as raunchy and disgusting as it was back in the 1990s (even more so, now that the fans who watched this as kids have grown up), so much so that it has a 12 rating in the UK (and the song "The Lord Loves a Hanging" song was cut, because the BBFC objected to portraying hanging oneself as a fun activity and not a painful, excruciating death) and Common Sense Media's website put this series as "Unsuitable for Anyone Under 15."
Signature Scene: The "Happy Happy Joy Joy" sequence from "Stimpy's Invention" is by far the most iconic scene in the series.
Song Association: Due to it using so many stock music cues, some of these pieces of music have become strongly associated with the series.
Uncanny Valley: That female anthro chihuahua with a realistic head (whom Ren falls for) in "Marooned".
Weird Al Effect: The LOG song is very well remembered from the show, but very few people realize that besides being a parody/homage of old toy commercials, the titular song borrows its melody directly from vintage Slinky commercials.
The "Loop of Death" music from an episode of Adult Party Cartoon is actually an old jazz number called "Hold That Tiger", and the recording used is from an old Betty Boop cartoon.
What Do You Mean, It's for Kids?: Just look up an episode. Any episode. You will be surprised when you find out that it was rated Y-7 during its airtime, while containing suicidal jokes, the use of the word crap and loosely censored "hell", racist jokes, tons of Getting Crap Past the Radar, Ren's disturbingly realistic mental breakdowns, homosexual undertones between the main characters, Body Horror, loads of Black Comedy and disturbing images, among many other things. Though, this could be sort of justified, since it aired in the early 90's, the era when it wasn't completely uncommon to have heavy themes in kid shows.
The Woobie: Stimpy, at times. Especially true in "Son of Stimpy" and "The Littlest Giant".
Ren counts at times too, though usually he's more of a Jerkass Woobie.
Both of them, in the episode 'Man's Best Friend'. Poor guys don't catch a break until the very end!
The frog from "Ren Seeks Help," who's on the receiving end of Ren's most sadistic moments.