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.
Badass Decay: In-universe: the Missing Link apparently once held his own against the navy, the national guard and some baywatchers. Until he beats up about thirty clones in hand-to-tentacle combat, that's very hard to believe.
Cargo Ship: B.O.B./Green Jello. A match made in mixers.
B.O.B. for the kids and the merchandise. Not really surprising he's the kid appeal character; he's the silliest looking monster, and the funniest character.
Dr. Cockroach hit it off with fangirls.
And there's the president, where every moment involving him is one of the most hilarious things you'll ever see.
Katie and Cuthbert, the One-Scene Wonder role reversal teens who encounter the aliens early in the movie.
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 anyway. God help you if you're on the fence.
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.
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.
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! * The Woobie:
Susan. After Derek dumps her, she looks so much like a kicked puppy.
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.
Tropes for the series
Designated Hero: Most of the time the titular monsters come across as idiotic xenophobic jerks, and there are several occasions where the conflict of an episode brought about by the monsters being assholes or just being plain stupid.
Hilarious in Hindsight: The Internet (who is actually an alien) constantly uses old and dead memes. This would be a groan-inducing attempt at being relevant...if not for the brief resurgence of extremely old memes at the time, making the episode look relevant and seem like a parody of current events.