Reuben's special skill has always been making sandwiches... until Leroy & Stitch, when he successfully repairs a space shipwreck and gets it off the ground. Making a sandwich or (any other snacks) is sometimes called fixing a sandwich, etc.
It just clicked: it's no coincidence that Hunkahunka and Drowsy's abilities can be undone with water. Just like their cousin Stitch, water is also their weakness.
In the episode "Babyfier", Lilo is trying to call a babysitter to look after her "babified" family. If one listens carefully, she's using the same inflection as in the first movie when she was explaining how bad it would be if she fed Pudge a tuna sandwich. It may seem like the show is trying to flanderize her argument from before. But this is more brilliant than it seems. What is Lilo arguing about? "Child endangerment". She doesn't want to leave her baby family members alone because remembers all too well that the last time Nani left her home alone, two aliens tried to capture Stitch and it lead to her house exploding. She doesn't want to risk that anything could happen to her baby-ʻohana while she's away.
In the movie, Stitch is sentenced to exile on an asteroid. In "The Asteroid", Stitch and co. travel to an asteroid to destroy it, only to find it inhabited by a lone alien. Now we have an idea about how he got there.
In "Mr. Stenchy", it's shown that Stitch lacks a Good Angelshoulder conscious, and instead has two Bad Angels. Since he wasn't designed to have one, Lilo became his voice of reason.
Spooky's number is 300, which can be read as "BOO". Appropriate for an experiment designed to scare people by transforming into your worst fear.
The four crossover episodes actually suggest good explanations for the series' little inconsistencies that wouldn't be possible to be explained otherwise:
The Night Marchers from "Belle" seem a little out of place in a sci-fi series since they are clearly ghosts, but if you take into account Jake Long lives in the same universe, they could just be magical beings that are on the run. This probably also explains the powers of the experiment known as Witch.
Technology like the 'automatic dehydrator' from "627" seem kinda odd... until you realize that they share the same world of Kim Possible, where Weather Machines are sold like cars. Who's to say that this isn't the same manufacturer or a similar fashion?
In fact, this could even explain Spinelli's father is revealed to be a secret agent in-universe, or whom Cobra works for now. Maybe both are agents of Global Justice from Kim Possible?
And it also justifies the existence of Warmonga and her people (along with the Area 51 aliens seen in Rufus vs. Commodore Puddles) in Kim Possible. It's the same universe of Lilo & Stitch, where extra-terrestrial civilizations are undoubtedly real.
Jumba's increased use of broken English in the series compared to the original film seems like Flanderization at first. Then I remembered that many of the human characters are also speaking pidgin English since it's spoken widely in Hawaii in real life. Evidently, Jumba has been on Earth long enough for local styles of speech to influence how he talks.
Mertle's Flanderization (becoming an even bigger Jerkass than she was in the first one, outright bullying her, etc.) seem rather odd, but then two things happen around the time the series ends. In Stitch Has a Glitch, which is an interquel set between Lilo & Stitch and Stitch! The Movie, Mertle mentions her father. Then Leroy & Stitch reveals that her dad "ran away". These two combined paint a more tragic explanation for her change in behavior: sometime between Stitch Has a Glitch and Stitch! The Movie, her parents got divorced. Confused and upset, she took her anger out on Lilo, causing her to become even more of a Jerkass than she was in the original film.
Lilo's seeming to abandon experiments or even giving them to Gantu in some episodes might seem like it's really out-of-character for her to do so. Then one might remember that in the original film, she spends so much time with Stitch trying to help him become a better person only for nothing to improve for her and him (or so it seemed before the climax hit), she runs out of patience with him, telling him to go away after he accidentally destroys her house in his fight with Jumba. It's pretty much the same ordeal in those episodes of The Series; no matter how hard she tries, those episodes' experiments were not getting any better. She ran out of patience during those times and decided it was not worth trying to help them anymore. (In fact, this was more obvious in some episodes than in others, such as in "Heckler" when that rude experiment insulted her and the "'ohana" and "one true place" phrases she loves.) Not to mention, she is a kid; children often don't have the best patience in the world.
It might seem odd that Gantu never really uses the threat of violence against Lilo or the other non-indestructible members of the ʻohana to force Stitch to give up experiments. After all, he was happy to bring Lilo along as a "snack" for Stitch in the original movie, and tried to send her to an alien zoo in Stitch! The Movie. However, Gantu has experienced firsthand what it was like to be up against 626 before he met Lilo: he has a better idea than anyone of how dangerous Stitch would be if he started playing for keeps. Plus, he still thinks of Stitch as a violent abomination: Gantu may not be the sharpest knife in the drawer, but even he isn't stupid enough to mess with the Morality Chain/Morality Pet of the super-strong, Nigh-Invulnerable monster that also happens to know where he lives.
Why was Lilo so adamant that Stitch wasn't responsible for all the destruction in "Phantasmo" even when he seemed to be caught red-handed? Because it's happened before. The last time Stitch destroyed things for no apparent reason Lilo did blame him for it, but it turned out to be because he was having seizures, and Stitch almost died in part because of Lilo pushing him away and him trying to flee to an uninhabited planet so he wouldn't be a danger to others. Lilo is determined to never make that mistake again.
Speaking of Phantasmo, experiment psychology from him might explain why Spike became good thanks to a hug. Like his cousin, he's never experienced something so basic as a hug. In part because of his own nature as a quilled beast that turns everyone silly. After experiencing something like that for the first time, it broke through that he could offer something better.
Despite being revealed that they are actually in the same universe, why didn't the various heroes help each other out outside of the most obvious reason? It is because they live too far apart for them to arrive on short notice, (long-distance) teleportation seems to be considered crazy even in such a world and two of the mentioned groups are civilians.
The Possibles and Stoppables live in Middleton. While it is not confirmed which Middleton it is, the most accepted answer is Colorado.
Finally, with Lilo and ʻohana in Hawaii, it is clear that unless the various organizations like the Dragon Council, Global Justice, and the Galactic Federation can cooperate, let alone set up hotlines in all the places stated earlier, the crossovers are clearly going to be a one-time thing despite the serious threats the world undergoes on a daily basis. The only known exception would have been the Lorwardian invasion, in which even then it was because of their forces landing on the various heroes' doorsteps rather than the heroes assembling.
While Angel's design has been criticized for being derivative of Stitch's, being a cuter Distaff Counterpart of him, it actually makes sense as to why she would be designed as such. Because she's a siren; sirens are meant to be beautiful and attractive as they use their beauty to trick or manipulate others. Angel was made to manipulate the other experiments, and thus Jumba made her attractive (by experiment standards) to help with her abilities.
"Woops" apparently shows Gantu managed to capture some of Mrs. Hasagawa's "cats". Given how much she loves them, imagine how devastated she was when it happened...
In "Spooky", Pleakley's worst fear is his mother. Given that Nani's worst fear is Lilo being taken away by Cobra Bubbles, you can only imagine the sort of vile shrew Pleakley’s mother was like.
Possibly jossed when we do meet Pleakley's mother in "Fibber", who's revealed to mostly just be the My Beloved Smother type—"Fibber" seems to confirm that Pleakley's real fear was disappointing his mother rather than his mother herself, and he successfully overcomes that fear after he finally just has an earnest conversation with her.
In "Spike," the poor little guy breaks down in tears after Pleakley hugs him. Was that the first time anyone had ever shown any sort of affection to him?
