Lightning Dawn, Rhymey, The Grand Ruler from My Little Unicorn. The sequel adds Goldwin to it, an Expy of Jeff from Today's Special, several episodes in My Brave Pony: Star Fleet Magic II are made specifically to involve him, even when they add nothing to the overall plot whatsoever. Subverted because while the author is willing to shout at everyone who makes fun of his characters, he does not care for the majority of them at all, ignoring them completely if he thinks that they serve no purpose for him anymore outside of battle scenes.
Mater from the Cars movies, at least to those who aren't fans of him. He received what was seen as a disproportionate amount of focus in the merchandise and got an animated series, Mater's Tall Tales. It got to the point that he effectively became the main protagonist of Cars 2. Definitely not helped by the fact that he's voiced by Larry The Cable Guy.
By extension, to some people, the Cars franchise may be this for Pixar. As if getting a sequel and loads of merchandise wasn't enough, it received a spinoff movie that had a theatrical release, Planes (which is not produced by Pixar, but rather DisneyToon Studios). It became followed by Planes: Fire and Rescue, which got a theatrical release as well.
One year, FOX's coverage of NASCAR races added a 'Digger Cam'—a ground-level camera in the infield that showed cars coming around a turn. The 'digger' part came from an animated gopher named Digger, who would pop up out of a hole, look behind him, notice the cars, scream, and then frantically get back into his hole. It was kind of funny the first time. After that it became progressively less funny. Then they did it repeatedly, every single race. This was the signal for FOX to render Digger in CGI, give him his own pre-race cartoon, and offer Digger merchandise. The response has escalated to three words: kill the rodent.
Digger was so beloved by FOX, they gave him a speaking cameo in the Alvin and the Chipmunks "Squeakquel", which was hated in its own right. Cue people storming out of the theater in rage.
It doesn't help that NASCAR actually ordered Fox to stop using Digger, blaming him for a decline in attendance of NASCAR races.
SportsCenter has the Mark Sanchez "Butt Fumble" which the network refuses to let be beaten in its "Worst of the Worst" competition. The hosts are sick of it, but the competition it goes against is usually something it can easily beat when there are funnier fails in the lowlight heel. It was eventually retired after 40 undefeated weeks.
The Big 12 conference and the Universities of Texas, Oklahoma, and Kansas. The favoritism of those three schools (the former two for having lots of money and strong football programs, the last for their basketball program and the former Big 8 headquarters being in Kansas City) has more or less (combined with front office instability) led to the near-collapse of the conference and four schools leaving. The conference defending Kansas' Jerkass attitude over the University of Missouri leaving (who had good reasons, such as the athletic department losing money due to the loss of football rivals Nebraska and Colorado) and the formation of The Longhorn Network (which is considered nothing more than a recruitment tool for Texas) only makes things worse.
It should be noted that most of the other big conferences had the same Pet attitude toward Texas and Oklahoma, as evidenced by the Pac-10's attempted recruitment of both schools AND their willingness to take any other schools they wanted to bring with them (Texas Tech and Oklahoma State). Not so with Kansas, as, had the Big 12 broken up, they would have been one of the remaining Big 12 schools with no conference despite the aforementioned highly successful basketball program, which could possibly justify their aforementioned attitude (Missouri's departure meant the end of Kansas' longest standing rivalry in basketball). In fact, the game of college football could be looked at as the Pet of the NCAA and universities as a whole given how it has solely driven the massive conference realignments in the past few years and how all the other sports programs must bend over backwards to accompany them (college football's huge popularity with US sports fans is the only thing keeping it from being a true Pet).
In Dino Attack RPG, Snake and Firecracker came across as being Creator's Pets, most tellingly because we were supposed to like them and their creator, Atton Rand, had little intention of letting them be anything other than Karma Houdinis in the end when everyone else wanted to see them locked up.
Arachne in the first version of Spiderman Turn Off The Dark was a HUGE Creator's Pet for director Julie Taymor. She got no less that three songs of her own (including one devoted to shoe shopping), supplanted the Green Goblin as the main villain in Act Two, and competed with Mary Jane as Peter's love interest. Julie insisted that not making Arachne's redemption arc the main focus of Act Two would ruin the artistic merit of the play and compared cutting any of her songs or scenes to a mastectomy. After Taymor was fired, much of Arachne's role was cut out via an extensive Re Tool, reducing her to The Artifact.
Same-character redecoes. It's common, in pretty much any action-figure line, for the later waves to feature an already-released character (usually the protagonist) with a different paintjob and sometimes a different accessory. This is generally meant as a cost-saving measure, since it's much cheaper than remolding an entirely new figure. Collectors and fans absolutely hate these things from the start: they're rereleases of something they already own, they're generally inaccurate in appearance◊ to the actual character, and they tend to look... well, stupid◊. This would be fine - just don't buy them and move on - except the stores tend to not be aware of this. Stores usually decide the figures that'll get put on shelves, and have a good deal of power in determining case assortments. Stores place much more stock in the most recognizable names, so they tend to request lots of same-character redecoes, which leads to more minor characters getting shortpacked or going completely unreleased. As an example, one Spider-Man line featured, in one case, three Superposeable Spider-Mans, three Hydro Blast Spider-Mans, three Dual Web Swinging Spider-Man, and one Sandman. This has the paradoxical effect of turning characters who are normally very popular in fiction into Creator's Pets on the toy shelves, with many a fan bemoaning their local store containing nothing but a solid wall of Spider-Man in tacky outfits. In the case of one series, the Creator's Pet status of the main characters in this regard was widely blamed for the line's cancellation - it turned out kids didn't want to buy three Claw Grabber Skeletors any more than the collectors did.
From BIONICLE, we have Vezon, to the half of the fanbase that considers himThe Scrappy. Greg Farshtey has admitted to Vezon being one of his favorite characters to write, and in the web serials, boy, does it show! Despite actually having very little to offer to advancing the plot, Vezon is almost always there to offer his Plucky Comic Relief antics, especially now that he has been fused with the Kanohi Olmak and has dimension-hopping abilities.
Bratz has Cloe and Yasmin, two dolls that are in nearly every single line and most other dolls are just slight variations of them. They're even considered one of the main reasons the franchise is slowly dying out.
Bumblebee became this after the release of the films. Being one of the star characters, he received a massive amount of merchandise and focus, and other series (Transformers Animated, most famously) were retooled to feature him. Being the Kid-Appeal Character, he naturally received a goodly amount of scorn, but his sheer overexposure quickly soured people on him; new redecoes of Bee developed a reputation for shipping at least once per wave and often three per case. His Transformers Prime incarnation was what tipped the scale into this - while Animated Bumblebee was a fairly tolerable Hot Shot clone, Prime 'Bee earned a reputation for being a Flat Character, constantly constrained from development due to having inherited the film version's lack of voice. Even the writers of the series seemed to dislike this, to the point of introducing Smokescreen as a more traditional Kid-Appeal Character and generally ignoring Bumblebee in most later plots. It's astonishing to consider that the 2007 Bumblebee toy was once considered a scalping target, when only four years later, 'Bee had actually earned a reputation for clogging shelves. It doesn't help that he's marketed more than Megatron, traditionally considered the second most iconic character in the franchise (next to Optimus Prime) before 'Bee hit it big.
The legendarily-bad Transformers Armada Side Swipe mold. When it arrived in stores, it was reviled as a fusion of every negative stereotype about the Unicron Trilogy: boring vehicle mode, badly-proportioned, overly-gimmicky, and poorly-articulated robot mode, with even the Minicon getting some hate. Hasbro wisely listened to the fans and never used the mold again... is what would be written here, if the mold hadn't gotten TWO reuses in the Universe line, AND◊ a heavy-but-unhelpful remold into Runabout. The last of these earned a particular ire for an Ensemble Darkhorse receiving the mold (and for having the wrong name, and for his partner not getting a similar release). It took three years for this mold to disappear from shelves... until Botcon 2012 offered a new version of him at premium price. Fortunately, it seems as if Shattered Glass Treadshot has finally broken the curse: he's basically the fantastic Reveal the Shield Jazz mold, with the color scheme and head of Side Swipe. The difference is striking.◊