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.
Hilarious in Hindsight: Dim's species was conceived as a fictional variety of rhino beetles. Eight years later it's discovered to be not so fictional◊ after all. Well played, nature.
Jerkass Woobie: Molt and Princess Atta, in two different ways. Also, the ant colony themselves during the Darkest Hour brought upon themselves.
Moral Event Horizon: It is unknown when Hopper crosses it. At first, his affair with the ants seems to be about food, and he seems Affably Evil when in a good mood. However, his attempt to feed Dot to Thumper has him come across as Faux Affably Evil. The next time he appears, it seems as though he's given up on his next planned raid of Ant Island on the grounds that the grasshoppers had more than enough food where they were. But then he remembers that one ant (Flik) had tried to stand up to him and, in a visual demonstration of a potential ant rebellion using the grasshoppers' grain storage, proceeds to kill a brace of henchmen by crushing them under a pile of grain. That, along with his "keeping those ants in line" speech, is enough to convince the grasshoppers that it was worth it to subjugate the ants after all. That said, he definitely crossed it by the time he ordered his henchmen to assassinate the queen.
Tear Jerker: Just after the Circus Performers save Dot, Princess Atta and Flik have a moment alone where Atta voices the pressure on her to rule the kingdom one day, saying that it seems like everyone is always looking at her as if they're..."Waiting for you to mess up." The way Flik says this isn't angry or overly sad, just kind of resigned and tired, in a way that should be familiar to anyone who has felt ostracized or under pressure. Atta even realizes the implication of this line, sincerely apologizing to Flik for the first time in the movie.