Stan's treatment of female hamsters other than his sister qualifies. Bijou is particularly uncomfortable when they first meet; she objects to him hugging her and refusing to give up her paw.
Adaptation Displacement: Other than hardcore anime fans, who has ever heard of the children's books?
Archive Panic: It ran for almost 300 episodes. Only 104 of those episodes were localized in English, and even fewer of those English episodes ever got released on home media.
Howdy is probably the most divisive out of the main Hams, with people finding his jokester personality funny or annoying and repetetive.
Stan, who was introduced a few episodes into the first season. Fans either love him or hate him for his constantflirting.
Sandy gets this as well, mainly for her treatment of Stan. She's either justified in stopping him from flirting or a hypocrite because she's in a relationship herself.
The movies. They have their own continuity together, but they're all so strange and don't fit with the rest of the show.
Later seasons had entire seasons' worth of episodes where the hamsters traveled to Lapis and Lazuli's world of candy, though this was dialed back for the final seasons.
It was very popular in Italy. Cristina D'Avena, who performed the Italian theme song (of this series and hundreds of other animes) made an album dedicated to Hamtaro in 2003, with 7 songs related to all the protagonists (including a shipping song about the Howdy/Pashmina/Dexter Love Triangle, no less).
It was also really popular in Canada, even getting exclusive merchandise there such as clothing and even Heinz pasta shapes!
"You hate me, right?"note This is a scene from episode 135 where Hamtaro have a bad dream about Laura, and the image was taken from English fansub Not to mention that now in the recent days you can see this scene on YouTube commonly (though not widely popular), but it was used in Mega Man Maker community by its infamous Malaysian forum troll Fanduber for troll purpose and to annoy peoples.
Kentaronote During a normal airing of Hamtaro in its early morning timeslot, somebody at Cartoon Network goofed and, instead of airing the second half of the episode, aired an episode of Rurouni Kenshin instead. Cue all the fanart of Kenshin as a hamster.
Moe: Pretty much all the hamster characters, being a series about Ridiculously Cute Critters, but special mention goes to Bijou, a sweet and feminine French hamster with Girlish Pigtails.
Never Live It Down: Most of the hate for the series in the west purely boils down to the fact that it aired on Toonami once. Even years after it no longer airs on it, it seems to be the only thing people can talk about in regards to the series.
The movies have a couple creepy scenes, including a devil-hamster (not Spat from the games) who can turn into a dragon.
One of the later seasons' finale had an episode named "Sweet Worm Surprise!", where the Ham-Hams traveled to Lapis and Lazuli's world of candy and were eaten by a worm that lived there. In the following episode, Boss had to free them.
Periphery Demographic: For every preteen kid that decried this show as a sign of Toonami's end times, there was another kid within the same demographic that admitted to liking the show or secretly watched and said nothing for years to keep up with appearances. There were also even those who didn't care a wit about anything else on Toonami who watched the show simply because they liked this type of show and, in some cases, knew some of the voice actors from other series.
Popular with Furries: The characters are cute hamsters after all, so the series has its niche.
The Scrappy: While Lapis and Lazuli have cute designs, most of the show's Seasonal Rot is directly attributed to them and Sweet Paradise to the point that they took over a majority of the show following their first appearances. They had to be dialed back significantly for the show to regain its slice-of-life elements.
Back when this show was on Cartoon Network, you wouldn't believe how many people fought over Hamtaro/Bijou or Boss/Bijou almost to the point of Die for Our Ship in some circles. Dexter/Pashmina and Howdy/Pashmina got this treatment as well.
Ships That Pass in the Night: Boss/Sparkle and Cappy/Penelope are fairly popular ships despite there being little romantic interaction between them, especially with the former.
Took the Bad Film Seriously: While it isn't a bad show, putting Hamtaro on Toonami was not one of the network's better ideas; it was completely out of place for the block and almost guaranteed a hatedom from the get-go. So when Executive Meddling gave them the show, the team went completely for broke on the promos, using a Peter Cullen voice-over in a completely serious tone over heroic hamster antics in a valiant attempt to make lemonade out of the lemon they'd been given. The resulting promos were actually pretty awesome, but also had little to do with the majority of the show.
Vanilla Protagonist: Hamtaro's defining trait is that he's a Nice Guy and he likes spending time with his friends, while his owner is a normal Girl Next Door. All of his friends have their own quirky personalities, all different from each other, and many of them also have interesting backstories.
Vindicated by History: The series was always well-received but it caught heat in America from older Toonami fans who wanted action anime, not cute hamsters. However, the eight-and-under crowd loved the show and it was a Pet Fad Starter for hamsters. As time went on, the younger fans that enjoyed the anime grew up and became vocal in their nostalgia. The reception of the series cleared up and it's known as a Toonami classic.
All the names have been changed and although most of the Japanese Holidays and folk tales have been kept, they too had their name changes. Yet, talk to the American fans and most of them will refer to the dub and not the Japanese version.
One episode that featured Kompeito was called "diamonds of sugar" in the dub.
The Italian dub added a rather peculiar reference joke: Cappy's owners were renamed Sandra and Raimondo, after the beloved married couple and comedy duo of the late Sandra Mondaini and Raimondo Vianello.