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.
Fanon Discontinuity: The English dub - what with censoring the ending and changing the names -doesn't exist to most fans.
Although, the English dub isn't too bad, seeing as it leaves her death in, unlike the German dub which removes it entirely.
Fridge Brilliance: Leafie's Heroic Sacrifice at the end is very easy to understand, if you see Leafie's primary motivation as being a Mama Bear. Having seen Greenie to fledging and knowing what she did about One-Eye, she helped another mother with her babies, the only way left to her. And One-Eye knows it...she's crying when she makes the final lunge for Leafie.
Squick: The conditions in the egg-barn, and the farm ducks' habits concerning their pond.
Tear Jerker: Quite a bit. The death of Wanderer, Leafie and Greenie's goodbye, and Leafie's death stand out.
Too Dumb to Live: Debatable. One-Eye refuses to scavenge, which leads to her nearly starving herself and her pups to death, despite the fact that we first see her near a pit full of dead chickens that could have easily sustained her family.
The big question is whether or not that pit is always that full of dead chickens, more being dumped in as others putrefy. The pups are obviously very young when we see them in winter, so the weasel was obviously just hunting for herself in the spring and summer (she probably wasn't even pregnant by then) and could afford to be pickier. If there weren't as many dead chickens in the pit (and this might be the case, since the chickens had the opportunity to run off during Greenie's rescue) in winter, the ones that were there were too far decayed to be edible, or the weasel otherwise could no longer reach it, that might be where her hardship is coming from. The film never addresses this.