Professor Membrane having robotic arms and saying how he lost them to sharks when he was young actually explains a lot about the episode Bad Bad Rubber Piggy. In that episode Zim messes with time to try to kill Dib in the past and ends up making Dib more and more crippled until Professor Membrane puts his son is a super powerful exoskeleton. Professor Membrane knows in that episode how his son feels and speared no expense in helping him.
Surprising yet fitting for a movie that is not just a long episode. One of Zim's plans actually works, even if it's stupidly borderline suicidal. The fallout reminds people how much of an actual threat Zim is, beyond being an overdramatic Woobie, and that he's still a homicidal alien maniac bent on enslaving and/or destroying the Earth, that hates all the humans on the planet. By making him the antagonist, it equally makes Dib the clear protagonist by actually defeating Zim and saving the Earth. What would be nothing out of the ordinary in any other movie is absolutely original in this one.
The Tallest don't want to change course, even when Earth and the Florpus are in the way. They're not just being stupid- in space, momentum is conserved, so the only things that actually cost fuel are slowing down and changing direction. By continuing straight, they're saving themselves from having to perform the complex maneuver that is a whole fleet changing course on short notice. Doing so when under immediate threat of Florpus, however...
Why does Clembrane have a stitched-up scar on his forehead? Zim probably had to operate on his brain to install any "programming" that would cause him to believe he was the real Dr. Membrane.
Professor Membrane’s character design here is noticeably bulkier than his design in the show, especially around the torso. This could be attributed to another major change in his character design - his robot arms. They’re probably much heavier than flesh and bone, so it’s basically like bench pressing all day, every day and built up his chest muscles.
It seems that Zim has finally learned how stupid people of earth truly are, a lot of his biggest mistakes early in the series came from grossly overestimating human competence and exaggerating measures to that. After several attempts at manipulating the population, it seems he has finally learned that's the most effective way to control the planet.
It also explains why Tak was so competent, as she figured immediately how much she could get away with and did it.
