Beetlejuice is the Ur-Example, coming just before Ren and Stimpy, and yet, not being as well-remembered. To tell the truth, it’s actually a lot tamer than most of these entries, since it was still the 80s and the show was (theoretically) trying to stay clean enough to avoid controversy. Fittingly enough, Nickelodeon reran it in The '90s, as a compliment to Ren and Stimpy and their other shows that exemplified this trope.
Family Guy regularly uses gross-out jokes as the basis of its humor. Frequently, characters are seen vomiting – often, extremely violently – after either legitimately falling ill, realizing they ate something that was inappropriate (such as horse semen that Peter claimed was milk but then revealed otherwise, all for his amusement) or being traumatized by having something revealed to them (such as Brian learning the woman he had sex with was a transgender person ... Quagmire's father(!)). The episode "Brian and Stewie" famously had Brian – after accidentally being locked in a bank vault with Stewie and thinking there were no more clean diapers in the baby's diaper bag – lick Stewie's dirty butt after pooping his diapers. (Stewie then reveals there were clean diapers in the bag and he just wanted to see if Brian would actually lick his butt; it makes Stewie throw up, then he tells Brian to eat that as well.)
Likewise, many other entries of Cartoon Network's What A Cartoon series went with that kind of humor. Most of those that were continued as their own series (like The Powerpuff Girls (1998) and Courage the Cowardly Dog) used it occasionally. There was also the Yuckie Duck shorts, which never became their own series.
Fleabag Monkeyface was all about fart, poop, and piss jokes. The main villain is even the host of one!
Dexter's Laboratory had plenty of this, from Dexter's chicken pox, to Dee Dee's germs getting all over his science lab room, to Dexter exploring his dog's insides, though still remarkably less so than other examples.
While Rocko's Modern Life was more satirical than gross, it had episodes dedicated to intestinal parasites among other things.
Beavis And Butthead derived this primarily from the duo's idiocy leading them to do all sorts of nasty things.
The Ripping Friends, one of the last series animated in the Kricfalusi style. Helps that it was made by Spumco (Kricfalusi's animation company) as well.
Drawn Together absolutely reveled in this. Sex jokes, toilet humor, vomit spewing, gorn, plenty of Gross-Up Close-Up, etc. Needless to say, you don't want to be eating while watching it.
Invader Zim was more well-known for its Black Comedy, but it had plenty of this as well. Mostly highlighted in "Dark Harvest", "Germs", and "Halloween Spectacular of Spooky Doom."
The Grim Adventures of Billy & Mandy had lots of this, with most of it originating from Billy (especially with his nose). Not that there aren't other things that can come from it though.
Aqua Teen Hunger Force: More so between seasons 5 and 7. The latter seasons downplay it to some extent.
SpongeBob SquarePants has always had mild grossout elements, with plenty of grotesque close-ups akin to Ren and Stimpy, but it really kicked into overdrive during seasons 5-7. Not only were entire episodes devoted to such lovely things as SpongeBob getting a splinter that becomes infected and swells to larger than his entire body, but Kafka Komedy and Black Comedy also became a common occurrence.
A number of Comedy Central originals like TripTank, Brickleberry, and Ugly Americans. Most made in vein with [adult swim]'s stuff and Family Guy. Special mention to Brickleberry, which features things like a winking moose anus and a bear drinking piss-infested water, among others.
On Aaahh!!! Real Monsters, a lot of the monsters' methods of scaring revel in this like being turned inside-out.
Grossology differs from most examples is that it's also an Edutainment action-adventure cartoon; meaning that while fighting villains themed around bodily emissions and putrid animals, the show aims to also explain why, exactly, you just vomited on the floor.
The Future is Wild animated series has some gross-out humor in its earlier episodes, though this is less because it aims to be a gross-out show and more because its a speculative science show that theorizes about far future lifeforms and environments, and doing that will naturally take you to some gross territory.
Mega Babies contains gratuitous, nauseating amounts of shitting, vomiting, and prolonged nose-picking. It's also by the creators behind SWAT Kats.
One needs an iron stomach to get through an episode of The Nut Shack.
Rugrats sometimes ventures into this. Kinda to be expected from a cartoon about babies though.
Total Drama does this mainly with vomit. There was even enough for Cartoon Network to run a marathon of it called "Total Drama All-Out Gross-Out". In particular, there are several episodes ("Brunch of Disgustingness", "I Double Dog Dare You", "Chinese Fake-Out", etc.) that revolve around disgusting food challenges.
South Park is definitely this, though how much it relies on it is often overestimated by its detractors. The show also has an in-universe example, Terrence and Phillip, which was directly inspired by a critic's review Matt and Trey read stating that South Park was nothing more than badly-animated characters telling fart jokes for 20 minutes.
Spliced had things like projectile snot, people being turned inside-out, and one of the characters growing a coat of mucus after not bathing for several days.
Korgoth of Barbaria: Gore to the extreme with every single joke based on violence. In fact, the reason why it only lasted a pilot was caused by a large chunk of the budget being used to animate blood and gore.
Fanboy and Chum Chum had fart jokes in the first season, but was toned down in its second and last season.
Some of KaBlam!!'s Life with Loopy falls under this, but Henry and June venture here on some occasions.
The Angry Beavers did this sometimes. In "Stinky Toe", Norbert gets a toe infection with no known cure; and at the end of "Norbert's Brother", Daggett suffers from a strange illness called "Gunky Ear".
Ed Eddn Eddy would venture into this occasionally, most noticeably with Ed:
Edd: Oh my...Ed, there's a new invention called SOAP. Have you heard of it?!
The bread-and-butter of Yvon of the Yukon, primarily engaged through its title character, a fat, unhygienic 17th-century Frenchman who wears nothing but underwear despite living in the middle of the Canadian Arctic. His disgusting habits, including frequent gassiness and an adamant refusal to bathe, are a major source of humor for the series, and episodes include "Parasite for Sore Eyes" and "I Thaw Your Butt". Heck, the intro even explains that Yvon was thawed out in the present by a dog urinating on the ice he was frozen in!
Almost Naked Animals. Ugly-looking animals in their underwear is just the tip of the iceberg.
Fish Hooks, especially concerning large (to the completely normal-sized fish) monsters.
The older, hand-drawn, episodes of Johnny Test. The Flash-animated ones mostly rely on slapstick with occasional run ins with this trope.
Adventure Time, despite being a somewhat serious show, has lots of poop, fart, and butt jokes. The show was also more than happy to have many a Vomit Indiscretion Shot.
Jimmy Two-Shoes is not as extreme as some examples but we get stuff like "Baby Boom", which involved a projectile vomiting infant, and "The Big Drip", which actually got banned from Disney XD for its plot being about a Potty Emergency. Then there was the time Lucius forced Samy to eat Misery Inc.'s new crud cereal product.
Most sketches in Robot Chicken involve either someone dying or someone shitting.
Codename: Kids Next Door in its early days before it became the action/comedy it's remembered as today.
Sanjay and Craig, big time. A show with episode names like "Unbarfable" and "Fart Baby" should say it all. Later seasons focus less on gross-out, however. (As the creators put it, "We wanted less fart, more heart.")
ChalkZone sometimes ventured into this territory, with episodes such as "The Big Loo".
Uncle Grandpa, with the pilot episodes featuring fart jokes, toilet humor (somewhat literally), a pimply, morbidly obese teenager sweating through his man boobs, and slightly cruder character designs. The show proper averts this for the most part, though, as it instead relies on a lot of Surreal Humor and in general just how weird things can get, plus the artstyle isn't as crude as it used to be. Most of the gross-out humor instead got used in the above mentioned Secret Mountain Fort Awesome (which UG's first pilot lead to the creation of), and it was probably because of that show's failure which would be why Uncle Grandpa instead became the surrealist comedy it is now.
Although aimed for preteen girls, The Buzz on Maggie featured some (the characters are houseflies for starters). However, its not as prominent as the promos made it seem .
Breadwinners. The show has the titular characters twerk in almost every episode and Buhdeuce has been shown to be able to travel via farting.
The 2015 Cartoon Network pilot Jammers. It's rather unexpected too, as it focuses on a group of teenage girls and the problems they face.
From the guy who gave us the aforementioned Almost Naked Animals and Fish Hooks comes yet another example of this trope: Pickle and Peanut. One episode is about a mutant butt zit to give you a taste.
Some of the episodes of the The Simpsons have elements of toilet humor. The Bloodier and GorierTreehouse of Horror series are good examples, notably "Treehouse of Horror XXII"'s "The Diving Bell and the Butterball", which revolved around Homer having to communicate by farting after an accident paralyzes him.
Matt Groening is evidently not above doing a little bit of this every now and then, as Futurama also had its share of toilet and gross-out humor, with many scenes of the Professor getting naked, a good chunk of the jokes on Zoidberg's character revolving around his revolting manners, a talking butt boil, and a pool filled with alien goat diarrhea and vomit. I Ate WHAT?! is also a common source of humor on the show, particularly in the post-cancellation episodes; Cubert eating rat kidneys, Fry eating Jrrr’s poop (mistaking them for M&M’s), and Leela unknowingly eating Fry’s kidney.
Animaniacs delved into this territory from time to time, such as Wakko's special salad in "Mobster Mash" and Slappy's plate of cockroaches and dung beetles in "Frontier Slappy".
The reboot features an even higher number of gross-out gags and Fan Disservice moments, such as the Warners licking a diseased pigeon to break a cuteness overload and a Trumplica cyclops using Odysseus as a loofa.
Judging by the pilot, Bamimation was going to be this, given that it involved Bam Margera and his friends. The pilot episode involved Bam Margera and Ryan Dunn shrinking themselves into Rake Yohn's body, in order to prevent him from hooking up with his disgusting, unattractive girlfriend.
Big Mouth is one of Netflix's biggest examples, with things like semen-covered crackers just scratching the surface. Considering the show is about puberty, it's at least fitting.
The Loud House has quite a lot of poop and fart jokes. When it's not either of those things, expect it to feature something else that's gross like boogers or, on occasion, puke.
The Cramp Twins is definitely this considering the numerous of fart jokes and other gross stuff that appears in this show. Most of the gross-out usually comes from one of the main characters especially Wayne Cramp. There was even an entire episode that involved him collecting spit from other kids!
The Crumpets contains a bunch of gross jokes, including but not limited to the protagonist talking baby's potty issues. One episode's resolution required him to press the bellies of bloated people so they can fart and become unbloated. And another episode reveals that the titular family has a hereditary big "pee-pee gland" affecting him and his grandmother!
Obscure Leslie Nielsen vehicle Zeroman definitely qualifies. The eponymous hero "flies" by farting, changes from his secret identity by going down a toilet, frequently battles villains themed around grossout humor (the first episode has him battle a giant robot resembling a butt that poops bombs), and even gained superpowered snot in one episode. Probably not that strange if you're familiar with Leslie Nielsen's fondness for that kind of comedy though (the man did put "Let 'er rip" on his tombstone).
Freaktown featured plenty of vomit, exposed butts, and consumption of gross things (like snot dogs and toe jam) from the inhabitants of the eponymous setting, which grossed out the denizens of Sweetlandia as much as it did the viewers.
The 1994 revival of Baby Huey delved into this while turning up the slapstick humor and adding in Gross-Up Close-Up shots. Naturally, Carbunkle studios, which worked on The Ren & Stimpy Show, was the main animation studio for this show as well.
Xiaolin Chronicles has some gross-out humor, mostly coming from Dojo. Nearly every time he senses a new Shen Gong Wu, his body gets covered with exploding rashes. At one point, he vomits almost on-screen. In another episode, he sneezes and his mucus freezes from the cold, then he tastes it. In at least two episodes, there's a Running Gag of him eating spicy snacks that make him burp. And so on.
F is for Family takes place in America during The '70s and portrays the economic and social hardship at the time as turning the country into a Wretched Hive that looks like one, gigantic Disgusting Public Toilet; with almost every building's crevice seeping with rust and grime (to the point that the ones that aren't decaying look disturbingly sterile) and every character finding themselves the butt of Toilet Humour at some point.
Bob's Burgers can reach this. The episode "Stand by Gene" had the kids go on a journey just to see a two-butted goat, and "Sacred Cow" had Tina thinking cows could express their feelings with their feces.
True to the magazine it's based on, MAD features plenty of gross moments; a massive glob of snot on a wall, a Gossip Girl parody involving a Vomit Chain Reaction at a party (one of the characters even vomits into the punch bowl!), Dora the Explorer getting carsick and repeatedly vomiting into her backpack, etc.
Most segments on Crashbox avert this, but the Revolting Slob segments take great pleasure in abusing this trope; so much so that they could put The Ren & Stimpy Show to shame.
The Owl House Not the entire point of the show (which is a Portal Fantasy coming of age story), but the setting of The Boiling Isles and some aspects of its magic system has some grotesque elements to it (no surprise there, since series creator Dana Terrace is a self-proclaimed fan of the macabre) and protagonist Genki Girl Luz is mostly un-phased by it being not averse to grossing people out (albeit due to social awkwardness rather than malice) herself.
. It's rather unexpected too, as it focuses on a group of teenage girls and the problems they face.