Die for Our Ship: Poor Sparky. While he isn't usually outright hated, because he gets a Ship Tease with Gadget in the episode he appears in his existence has been known to make quite a few Chip/Gadget or Dale/Gadget shippers uncomfortable.
Gadget Hackwrench. She was for a while Disney's most popular female character, surpassing Minnie Mouse and Ariel. She is still the most popular character out of this series by a mile. The fact that she has her own cult in Russia (see Testosterone Brigade below) pretty much helps.
Foxglove the Bat, despite appearing in only one episode, has an enormous cult following, eventually earning her own website which still exists to this day (though it hasn't been updated since 2000).
Just like Foxglove, Lahwhinie appeared in one episode but gets an impressive amount of spotlight in fanfics and fanart.
Fandom Rivalry: Fans of this show tend to harbor a resentment towards Bonkers for replacing Rescue Rangers in the time slot.
Fanfic Fuel: Most prominently, the scenes in "To the Rescue, Part 3" when Monty and Gadget talk about Geegaw, leaving the viewer with more questions than answers, and the end of "Good Times, Bat Times" which leaves the Dale/Foxglove pairing unresolved.
The death of Gadget's mother (who went unmentioned in the series, and has been given many different names) and father (who was only mentioned in the pilot). There's been countless theories created by the fandom, but pretty much everyone agrees that Gadget's mother died well before Geegaw. The latter is usually considered to have been killed in a plane crash.
The one great debate is not about whom Gadget shall be together with. It is about whether ("pro") or not ("anti") Gadget shall be together with Chip. No matter whom she'd end up with, if anyone, if not with Chip. The majority of fans, by the way, seems to be in favor of Chip/Gadget.
Prior to the premiere of "Good Times, Bat Times", Dale and Gadget were the major Fan-Preferred Couple.
You'll notice not many people ship Gadget with the One-Shot Character Sparky, a lab rat and basically Gadget's equivalent to Dale's Foxglove; a one episode Ship Tease. This is basically the pairing pros and antis can both agree to dislike.
The voice Jim Cummings uses when he plays Monterey Jack's father Cheddarhead Charlie on the episode "Parental Discretion Retired" is actually the voice Cummings used to play Monterey Jack after Peter Cullen left the show. "Parental Discretion Retired" was one of the early episodes that had Monterey Jack voiced by Peter Cullen.
In "A Wolf in Cheap Clothing", Jim Cummings voices a Tasmanian devil. A couple of years later, Cummings would become the voice for theTasmanian Devil (as in, the Looney Tunes character).
Monterey Jack talked a lot like Steve Irwin already before the latter was even known outside Australia.
"A Chorus Crime" features large quantities of penguins tap-dancing on the ice—five years before Happy Feet.
In the episode "A Lad in a Lamp", the genie is voiced by Dan Castellaneta. The episode predated Aladdin by three years and is funny because Dan Castellaneta would become The Other Darrin for the Genie in the Aladdin animated series due to Robin Williams having a dispute with Disney.
"Prehysterical Pet" features a space-traveling Stegosaurus. In 2005 came Astrosaurs, a British children's chapter book series which is about space dinosaurs and has a Stegosaurus as the main hero.
Ho Yay: Dale during the drag act in Adventures of Squirrelsitting. He's clearly enjoying his disguise and is flirty with both Chip, Monty and even Fat Cat.
Monty: I'm sorry, pallies. But Gadget needs some cover.
Dale: No problem! (winks and rotates his shoulder)
And then there are the episodes "Adventures in Squirrelsitting" and "Good Times, Bat Times" where even more people are here for Tammy and Foxglove respectively.
Moe: Dale is best described as a playful puppy dog trapped in the body of a fuzzy, adorable chipmunk. His softer temperament than Chip makes him seem cuter in comparison.
Moral Event Horizon: Fat Cat crosses it in 'Adventures in Squirrelsitting' when he threatens to drop Tammy and Bink to their deaths if he doesn't get the Maltese Mouse and even when he gets what he wants he drops them. Thankfully, Chip and Dale are there to save them.
Foxglove from "Good Times, Bat Times". Foxglove has an entire website devoted to her (and now dedicated to her voice actress, the late Deborah Walley).
Tammy and Bink from "Adventures in Squirrelsitting".
Queenie from "Risky Beesness".
Sparky from "Does Pavlov Ring a Bell?"
Lahwhinie from "Gadget Goes Hawaiian."
Geegaw Hackwrench from "To the Rescue, Part 3" isn't even really a character, he is only ever shown on a picture. Yet, despite his unknown fate and total personal absence, he is quite popular in the fandom.
Popular with Furries: The fandom contains a lot of furries, many who consider the cartoon their Gateway Series. Especially Gadget who is a fan-favorite (Disney was honestly surprised with her popularity).
The Scrappy: Canina La Fur from the episodes "A Chorus Crime" and "They Shoot Dogs Don't They" is probably the most hated recurring character due to her diva-esq personality and the fact that she can be Too Dumb to Live at times. Despite that Monterey Jack saved her in "They Shoot Dogs Don't They", she was still rude to him and never got his name right.
Shipping: Chip/Gadget, Dale/Foxglove, et al. If there's even one hint of a ship in the series, someone's supported it somewhere in the fandom.
Ship-to-Ship Combat: The debate over the Chip/Gadget ship led to two flame wars known as the Ranger Wars (one in 1997 and the other in 1998), and it will probably never be settled.
Smurfette Breakout: Yup. Gadget. Even twenty years after the show ended, there's still a Gadget themed roller coaster at Disneyland. Disney admits that they had no idea she would be such a hit.
Gadget can have amazing Woobie appeal when she loses confidence in her piloting or inventing skills, such as in "To the Rescue" and "The Case of the Cola Cult".
Dale counts considering how much he's made fun of, and is hurt in the process. He's get hit with this in "Double O Chipmunk" and gets hit with it even harder in "Le Purrfect Crime" where Chip scolds him to the point where he's in tears.
Pity poor Sparky the lab rat. He genuinely believes his owner Professor Nimnul is a good guy, only wants to use science to help people, develops a crush on Gadget... and has no memory of the awful things he does while under Nimnul's control. He's pretty horrified when he sees the results of his actions, and although it's played mostly for laughs, in hindsight it must pain him deeply to learn he's been used for evil purposes and that the man he admired was evil.
Zipper in some episodes, especially in "Zipper Come Home".
Flash The Wonder Dog. He's a skittish and neurotic animal actor who gets framed for awful crimes just because of his species.
The unnamed bear from the "Bearing Up Baby" episode. He's just a sweet and lonely bear who wants a friend but throughout the episode, he's a Badly Battered Babysitter who ends up getting chased by a bunch of angry, armed hunters who see him as a legit threat. The tears that poor bear sheds when he has to give up the baby just makes you want to give the guy a hug.
Ku-Ku the gorilla from the episode "Gorilla My Dreams" spends most of the episode crying over her missing kitten and committing robberies for Fat Cat so he won't hurt Dale.
Anticlimax Boss: While the first game as a whole isn't too hard, a number of the bosses (including Fat Cat) barely move at all, and are highly predictable.
Even Better Sequel: The second game isn't as well known due to being released so late in the NES's lifespan, but it improved on the first in nearly every way possible, from graphics, to gameplay, to having a story that would not be out of place in a multi-part TV episode.
Game-Breaker: In the second game, proper use of the fastball special makes most bosses incredibly easy.
That One Level: The final level of the first game greatly cranks up the difficulty. Most of the level takes place on conveyor belts that mess with your character's speed and make it difficult to move, which is especially troublesome during points where you have to make some difficult jumps with your moment hampered. There are no stone blocks for you to carry around constantly to protect yourself with. Not to mention that the enemies in the second half of the level have the ability to fire projectile weapons, and if they do they can destroy your boxes if you attempt to hide in them, which will leave you defenseless. Be prepared to die at least a couple of times before you finally reach Fat Cat.