These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel: The movies have a couple creepy scenes, including a devil-hamster (not Spat from the games) who can turn into a dragon.
One Japan-only season finale had an episode where the hamsters traveled to Lapis and Lazuli's world of candy and were eaten by a worm that lived there. 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. You people know who you are.
Stan who was introduced a few episodes into the first season for the Base Breaker reasons mentioned above.
The second opening theme. For reasons unknown, Cartoon Network hated it and refuse to air it, opting to air the first theme over the second season episodes. However they accidentally let it slip with a few airings, which left a few fans scratching their head in confusion. Soon it was found out that other networks worldwide that airs the English version of the show do air the second opening theme. Cue Keep Circulating the Tapes, as a number of fans do find the second theme better than the first one. And even then Cartoon Network is trying to stop the circulation by immediately flagging the videos off YouTube as soon as someone uploads it. A few mp3 copies have been known to circulate the web, despite this.
Mondegreen: The second season theme is so fast-paced and contains so much ham-speak that it's not unusual for transcriptions of it to often get at least some of the lyrics wrong.
Ship-to-Ship Combat: Good Lord, 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. As well as Travis/Laura and Roberto/Laura (yet Laura does not like Roberto at all.)
All the names have been changed and although most of the Japanese Holidays and folk tales have been kept, they too had their names changes (Urashima Taro became Leo in the dub). Yet, talk to the 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.
Hamtaro: Ham-Hams Unite! has one which depends on which way you take to get Dexter and Howdy in the clubhouse. Either Dexter will help Howdy who gets stuck in a cash register or Dexter will become frozen alive in ice and Howdy must thaw him.