The villains Grim and Hildy Gloom from The 7D often behave this way towards each other when they're alone, on one occasion when the dwarves snuck into their hideout to take back the Spring Chicken Grumpy got so sick of their lovey dovey talk that he told them to knock it off, giving away their hiding place in the process.
Amphibia: In "Sprivy", Sprig and Ivy are dedicated to spending as much time together as possible and doing it while being cute, much to the annoyance of other resistance members. They eventually agree to dial things back a bit after their couple shenanigans nearly lead to a mission ending in disaster.
Archer: In season 6, after Lana and Archer get back together, their "smooch-boochy"-ing is so insufferable the rest of the cast plot to break them up (after Pam vomits in her crock-pot).
Jérémie and Aelita from Code Lyoko can sometimes slip into this. They do have fights or misunderstandings a few times, but it is always resolved by the end of the episode.
It turns out that in romantic moments (specifically in his affair with Morganna) Darkwing Duck is just as inclined to flowery vocabulary and corniness as he is during crime-fighting.
Ed, Edd n Eddy: In the Valentine's Day special "Hanky Panky Hullabaloo", Edd and May Kanker end up falling in love, and their repeated gushing over each other with cutesy pet names drive both the other Eds and May's sisters up the wall.
A featured couple who ran the candy company Romanticorp.
Fry and Lucy Liu-bot from "I Dated a Robot":
Lucy Liu-bot: You're cute! Fry: No, you are! Lucy Liu-bot: No, you! Fry: No, you! Professor Farnsworth: Oh dear! She's stuck in an infinite loop, and he's an idiot! Well, that's love for you.
Again, Fry and Colleen in The Beast With a Billion Backs, much to Leela's disgust.
Fry: Well, got to skedoodle-oodle. We're taking a cuddle-cab to Hug-a-Bunny Village!
Ronaldo: (while talking on the phone) "Oh, just a second, honey..." (yells at kissing couple beside him) "YOU KNOW THERE IS SUCH A THING AS TOO MUCH AFFECTION!" (goes back to his phonecall) "See you soonsies!”note The couple in question were of course... Kick and Ronaldo's girlfriend (whom he was talking with on the phone), Kendall.
The Legend of Korra: Mako and Asami are this way for a time, although they're not as bad as some of the other couples on this page. Korra is especially disgusted when the two of them Eskimo kiss or wink at each other and blow kisses from across the room.
Mako: These new uniforms look great! Asami:You look great, champ!
Episode nine is about when they start moving away from this type of relationship, as they eventually break up and turn into good friends instead.
In a rare platonic example, gophers Mac and Tosh from Looney Tunes act even more buddy-buddy than the likes of Chip 'n Dale, to the point that it gets on the nerves of characters In-Universe.
The Loud House: Lori "Babe" Loud and Bobby "Boo-Boo Bear" Santiago's relationship, if their respective younger siblings Lincoln and Ronnie Anne's reactions to it are anything to go by. In one episode, Lincoln and Ronnie Anne are so exasperated by their respective older siblings' Inelegant Blubbering that they have to pry them apart from each other.
Although not a complete example of this trope, there is one episode of My Life as a Teenage Robot in which Brad is about to be married to an alien who refers to him as "Bradley-Boo." Squick.
Big Macintosh and Cheerilee act like this in the My Little Pony: Friendship Is Magic episode "Hearts and Hooves Day", thanks to a love potion provided by the Cutie Mark Crusaders. They spend nearly half the episode staring into each other's eyes and calling each other cutesy pet names like "Schmoopy Doo", and even the Crusaders - who'd hoped for sparks to fly - are visibly disgusted by their constant lovey-dovey talk. This is the point at which they check their work and realize what a horrible mistake they've made. They didn't make a love potion, but a love poison. They managed to keep them apart for a period of time to wear out the spell.
Professor Utonium and Miss Keane become this in an episode of The Powerpuff Girls (1998). They break up when it turns out that he doesn't like her cat.
Ready Jet Go!: Carrot and Celery are Happily Married and boy do they love to show it. In the earlier episodes, they flirted a lot to the point where it occasionally made the kids uncomfortable. In "How Come the Moon Changes Shape?", Jet and Sean were so grossed out at their love song, that Sydney and Mindy punched them for disliking it. Ironically, Jet and Sean themselves would go on to have Ship Tease.
Regular Show has both a straight and literal example with Muscle Man and Starla. They constantly used pet names and were overly affectionate. Emphasis on overly; they would commonly disgust those around them when engaging in PDA.
On The Simpsons, Ned and Maude Flanders frequently verge on this territory. At a marriage counseling group-therapy retreat, Ned reveals the sordid truth that "Well, sometimes she highlights passages in my Bible instead of her own!", to which Homer rolls his eyes and says, "It's a good thing you don't keep guns in the house!"
A few episodes into the 20th season of South Park, of all the possible characters, Cartman and Heidi Turner end up becoming this. It's exactly as strange as it sounds, and the entire student body at their school falls into a stunned silence upon finding out about it.
Rafael and Angie Diaz, Marco's parents from Star vs. the Forces of Evil are usually seen as a lovey-dovey couple. In Star and Marco's Guide to Mastering Every Dimension, Star says that they can be usually be found cuddling on the couch. In the "#Marco LIVE Animated Live Chat", Marco said in response to a fan, they were high school sweethearts and loved each other for a long time. These episodes show how the Diazes are lovey dovey.
"Diaz Family Vacation": Rafael and Angie give each other bedroom eyes on the couch and Angie plays with Rafael's chest hair. In the Forest of Certain Death, Rafael comments on his wife's beauty. And while they were in the hot spring, they make kissy faces to each other.
"Raid the Cave": As Star uses the All-Seeing Eye to find Glossaryck, Star has spotted them by surprise as they pop their legs up and they lean in to kiss.
From Steven Universe, Ruby and Sapphire, though they don't get much of a chance to show it since they're fused as Garnet the vast majority of the time. But when they do, they flirt outrageously (and call each other corny pet names like "Laughy Sapphy") and shower each other in kisses, to the point where Steven blushes and has to look away.
Further shown in the episode "Hit the Diamond" where Steven, Garnet, Pearl, Amethyst, and Lapis Lazuli have to play baseball against five Rubies. When Garnet unfuses so that "our" Ruby can pretend to be on the opposing team, Ruby and Sapphire flirt repeatedly, to the point of both teams' annoyance and the ruination of Steven's plans.
Newton and Kimmy sometimes act like this on Sym-Bionic Titan, calling each other names like "muffin cup" and "honey bear."
Hugh and Jean in Taz-Mania, at times. Taz and Drew certainly seem to think so.
Geoff and Bridgette in Total Drama Action become so annoying that they're the first ones voted off.
In the Grand Finale of All Stars, Heather and Alejandro of all people become the Unholy Matrimony variation of this trope. It gets to the point that both of the former antagonists are uninterested in helping out Mal, and Chris changes the rules just to make them stop. The creators, however, have stated that Heather and Alejandro are still an Official Couple.
X-Men: Evolution: Once Scott and Jean finally get together, Kurt and Kitty gleefully mock them as being this by going full out daytime-TV.
Though they usually fit this trope in any of their appearances.