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.
YMMV: Monsters vs. Aliens
Badass Decay: The Missing Link apparently once held his own against the navy, the national guard and some baywatchers. Until the climax of the movie, that's very hard to believe.
According to his website profile, he was a real badass. Until 30 years ago. Probably out of his prime at that point.
Not to mention he's been cooped up in Area 52 for several decades. Note the beer belly.
In the Tv series they seem to have had him working out in the interm. Not much more effective, but less beer belly.
Cargo Ship: B.O.B./Green Jello. A match made in mixers.
Complete Monster: Gallaxhar. Humourous sarcasm and hamminess aside, this guy lets his obsession with obtaining Quantonium drive him to unleash a huge robot on San Francisco, which probably would have endangered everyone there had they not already been evacuated. Upon learning that the Quantonium is within Susan, he has no qualms about almost killing Insectosaurus to get her and forcibly drain it out. All this to fuel a machine that creates an army of clones of himself in order to wipe out most of humanity and enslave those left as lab rats. His motive? To rebuild himself a new homeworld, because he himself destroyed his original one and everyone on it. His barely-revealed backstory hints that he has a Freudian Excuse or two, but it's strongly indicated that they are too poor to excuse his actions in any way. By the end, you can be sure he thoroughly deserves getting blown up with the rest of his ship.
Kaite and Cuthbert, the One-Scene Wonder role reversal teens who encounter the aliens early in the movie.
Fetish Fuel: Where to start?! The movie should have been titled Viewers Vs Fetishes. Only a few minutes in, and our attractive female protagonist grows to 50 feet tall against her will, wedding dress tearing, straps popping, moaning the whole while and begging for it to stop. Then, over the course of the movie, she is strapped down with steel cables against her will and drugged, assaulted by a giant robot and an alien with tentacles, electrocuted and caged repeatedly. Twice she wakes up in different clothing (skintight leather at one point) and she nearly kisses her fiance's head off. Not to forget the camera angled at Susan from below, capturing her gigantic bottom in glorious 3D... Is this really for kids?
From the sound of it, Gallaxhar outfitted his computer with the voice of a sexbot. Just imagine the countdown in a different setting...
Ship-to-Ship Combat: The fandom is a bit split when it comes to who Susan gets paired with. Given the lack of Token Romance within the film, many tend to gravitate towards Dr. Cockroach/Susan since he takes an active role in trying to reduce her size and they seem to converse the most (also, they're the only two monsters who used to be human). But Link/Susan has its share of fans as well, considering that Link's whole deal is that he chases beautiful babes anyways. God help you if you're on the fence...
The whole ship-to-ship combat situation for this fandom is not that bad. There are at least fans who can tolerate both points of view on the matter no matter which side they're on (if they're even on one in the first place). There are plenty of fandoms that are much worse..
Shout-Out: The whole plot premise could be considered a shout out to the Wizard of Oz movie. Think about it. A MacGuffin girl (Susan/Dorothy) taken out of her normal life and set on a quest to defeat a Big Bad (Gallaxhar/the Wicked Witch) via clingy Phlebotinum (Ruby Slippers/Quantonium) with three male friends who double as a power trio (Link, Dr. Cockroach, B.O.B./Cowardly Lion, Scarecrow, Tin Man) plus a pet-like animal (Toto/Insectosaurus), is captured by the Big Bad so needs to be rescued by said friends who do so by pretending to be part of the Legions of Terror (complete in Monsters with B.O.B.'s almost direct "I may not have a brain but I have a plan" quote).
Tear Jerker: C'mon, Susan reached Buffy level Woobie-ness when she arrived at Area 52. Then there's Link with Insectosaurus as he's shot... "Don't you close your eyes on me! Don't you dare!" and staying with his body from night till dawn.
Also B.O.B failing to realize that he, Dr. Cockroach, and Missing Link were all going to be blown up on the alien ship soon after and cheerfully telling them "see you tomorrow for lunch!" Instead of correcting him, the doctor and Link smile and tell him that they'll be having candy, cake, and balloons at that lunch.
Ugly Cute: Pretty much all of the other monsters aside from Susan herself.
Uncanny Valley: The stylized inhuman "Monsters" are a bit easier to watch than the actual humans.
To paraphrase the movie description at the top of the page, aside from the monsters, all the humans basically look like live action versions of the humans you'd see in mags like Cracked or Mad. Kinda off-putting at first, but you get used to it.
Viewer Gender Confusion: Insectosaurus. The movie calls the monster a "he", but a behind-the-scenes book lists the monster as a female. This has lead to a Broken Base amongst the fans of the movie as to which is truly canon regarding the monster's gender.
If Insectosaurus was only a larva before she metamorphosized, then it may not have even had a gender or anatomical indicators thereof. Calling it "he", as with B.O.B., could've been purely a convenience.
What an Idiot: Derek dumps Susan for the sake of his career without considering the worldwide fame their continued relationship would bring him, not to mention the millions of dollars in book deals and movie rights. Sure, he'd need a raincoat to have any hope of ever pleasing her, but it's still a very stupid decision from someone who's already been characterized as a selfish asshole. He does put things together, sort of, when he forgives her and offers to take her back at the end. Of course mentioning that he was offered a network slot if he got an exclusive interview in the next sentence made Susan doubt his sincerity. Letting that detail slip only reinforced his stupidity.
Susan: Are the cameras running, sweetie? Derek: Why, of course they are! Viewers (facepalm)
According to the commentary, one possible (deleted) follow-up to Derek dumping Susan has her going on a rampage through town to try and crush Derek. It would have been somewhat out of character for Susan to do this at this point of the movie, but that doesn't remove the fact that she could have done it, thus further reinforcing Derek's idiocy.
The Woobie: Susan. After Derek dumped her, she looked so much like a kicked puppy.
"I don't want a poster. I want a real kitten, hanging from a real tree."
The monsters, after they scare off the party.
Link. The poor guy gets his butt kicked several times during the battle against the robot probe, and even gets knocked out after it's already been defeated. He was so obviously downbeat about his performance that one almost expected him to do a Face-Heel Turn.