Why does Tiny the Tyrannosaurus fall into line quickly after the mini-Doris is knocked off him, and why does the Robinson estate have an octopus butler and a dog that wears glasses? Apparently, animals on the grounds tame down quickly and get Amplified Animal Aptitude. And why would Lewis invent that? To give Franny her dream of singing frogs.
Sort of a Fridge Heartwarming as well, but the frogs have miniature clothes, instruments, and their own tiny frog bar complete with a specially-designed fly vending machine. Cornelius created all sorts of amenities specifically to make Franny's frogs feel at home in the Robinsons' house.
Why is Franny so very moved when her son tells her that his new friend Lewis is an orphan? Because she's married to a former one, and personally knows from his example that it's a rough way to start out in life.
This also explains (explains; not justifies) Wilbur's casualness in relating Lewis being an orphan. Growing up with a dad who was one has made him think of being an orphan as being no big deal since it worked out well for his dad. He just doesn't understand.
Also, the future seems to be significantly Sugar Bowl-esque, so child homelessness must be very rare in the future. Especially considering Lewis had to go through being an orphan, is very kind, and can now impact the world to the point where he can prevent other children from becoming orphans as well, or at least make sure orphanages weren't the underfunded dead-end they were when he was there.
Wilbur Robinson's appearance resembles Franny more than Cornelius because if he looked like Lewis and went back into the past to prevent the Bowler Hat Guy from ruining his dad's future, the fact that he resembles Lewis would have been a dead giveaway to Lewis that something odd is going on!
Genetically, it makes sense that Wilbur would have some of his more obvious traits from Franny. Brown eyes are dominant over blue, and dark hair tends to be dominant over light hair. Franny and her brothers are Italian-American, so it's likely they are all homozygous dominant (meaning they possess two dominant genes and thus can't pass along recessive genes) for hair and eye color. But Wilbur does appear to have his dad's jaw and ears.
Franny tells Lewis that she is "always right", and Cornelius advises him to "go with it". Later, when Lewis meets the younger Franny, he gains her affection by telling her that she's right about her hobby of teaching frogs music. The older Lewis/Cornelius and Franny probably remembered that moment.
Wilbur claims his dad looks like Tom Selleck. Maybe he's aware that he sounds like him, and that's what first came to his mind when Lewis asked. And why does Lewis ask what Wilbur's dad looks like in the first place? It wasn't just Leaning on the Fourth Wall; he's a visual thinker.
Wilbur doesn't look like a kid from the future and Lewis has some trouble believing him. When they go to the future, Wilbur puts a hat on Louis so no one will recognize him as a kid from the past. Why would his family think that he looks like a kid from the past if people in the past couldn't recognize a kid from the future? They wouldn't recognize any kid from the past, only Cornelius because of his Anime Hair that he still has.
Bowler Hat Guy's decision to use a dinosaur to grab Lewis makes more sense when you remember that young Goob's baseball team was the Dinos. If he had succeeded, it would have been poetic justice to take his revenge using a dinosaur.
Lewis' adoptive parents being scientists makes sense in terms of family matching, but it also helps preserve the twist. When we're introduced to Lewis' future adoptive mother, she's going by the name Dr. Krunkelhorn. Presumably, "Krunkelhorn" is her maiden name and "Robinson" is her married name. People who write academic papers often don't change their names when they get married to minimize confusion, so the fact that Bud and Lucille lean towards academic provides another way of hiding that they're Lewis' future parents.
When Lewis is first explaining his project to the judges, Dr. Krunkelhorn says, "Wrap him up, I'll take two," as a joke. But it also hints that: 1. Lucille had already taken a shine to her future son before the invention worked, because Lewis's adoption was never about him being successful but about finding the right couple and getting out of his own way, and, 2. At the end of the movie, there are, briefly, two Lewises — the child and adult versions.
Apparently in the Bad Future, Doris did something to Goob after taking over. After a little while, the brain machine POWERS OFF like static. Who knows if the brain was just attached to the machine after Doris KILLED Goob?
Milder example, along the lines of Fridge Cringe. When Franny asks Wilbur "What did he mean 'if' he had a family?", Wilbur is totally casual when he replies that Lewis is an orphan. He probably should be glad Lewis didn't hear him.
Subtle, but no one seems to see anything wrong with Lewis calling "North Montana", "Canada", despite his saying that he supposedly lives there. The most likely reason for this is that a lot of the people there didn't like the union/annexation and insisted on calling it Canada. Hence, the lack of follow-up on that was because it was still a politically touchy subject.
Unlikely; they wouldn't have said "Nobody calls it Canada anymore" if Lewis had already shown preference to calling it 'Canada'. Far more likely it was a peaceful union and both names were in common use for a while until "North Montana" took over as the dominant one.
Tallulah says it "hasn't been called Canada in years". Given Lewis is 12 and Wilbur is 13 at the time of the movie, the Robinsons' future could be as little as twenty years ahead of Lewis' childhood. The Northern Montana territory was probably a recent merge by the US and Canada—it's entirely possible the schools haven't got around to teaching about the merge in history quite yet, hence the gentle correction.
Petunia is a puppet on Fritz's arm. Despite this, she's verbally abrasive, and even physically abusive at one point. Two points immediately become horrifying in hindsight.
The family just kind of...takes this in stride. Despite everyone else's general wackiness, Fritz' tendency to harm himself should raise at least an eyebrow or two.
Fritz and Petunia have two kids. There is a very real chance that the Petunia puppet is based on Fritz's deceased wife, and he's completely unable to move past her death...even though she seems like a terrible person towards him.
Either the puppet is a remnant of Fritz's dead wife, or the kids are adopted and Fritz has some sort of harmful multiple personality disorder that makes him abuse himself with words and mild violence. Neither option is...pleasant to consider.
There was a deleted scene in which Lewis takes Bowler Hat Guy back to the past with him to give him the chance to wake a younger Goob up in time to catch the ball, an offer he accepts with heartfelt thanks as he disappears from existence. Compare that to what actually happened in the movie, in which a nervous Bowler Hat Guy disappears leaving his trademark list behind, the final item being a question mark. Lewis later goes back to the past alone, and wakes Goob up himself, thusly flinging Bowler Hat Guy headlong into nonexistence. Keep Moving Forward!
Actually he's probably happy somewhere, maybe playing baseball. He didn't erase him from existence unless Goob died between then and then.
To explain, the Bowler Hat Guy was necessarily erased in that he no longer exists. Because Goob woke up, caught the ball, and won the game, chances are that his life is going to go into a different direction. The Bowler Hat Guy still exists, only he's not the Bowler Hat Guy, he's just an adult Goob who'll have probably had a better life.
The short "Pet Project" ends with Bowler Hat Guy still around, in the first version, he's in an insane asylum and in the other version, he's telling the story to the Robinsons who decide to bring him into the family...and give him the duty of taking care of Tiny the T-Rex and his enormous litter box!
In the Bad Future, Lewis is attacked by the Robinson family, now mind-controlled by Doris. Wilbur, who had been sucked into nothingness, isn't there...but neither is Cornelius. Doylist explanation: they didn't want to spoil the twist. But the In-Universe reason may be much, much darker, given Doris' hatred for her creator...
The fact that all that's left of the very first time machine is a single nut is kind of unnerving considering that this implies that the rest of the machine was either so damaged it wasn't safe to keep around or outright got vaporized into nothingness.
There's a darker message underlying that last thing (?) that Goob/Bowler Hat Guy writes: he doesn't know what to do with his life, because he has nothing. He has no loved ones to fall back on, no career prospects, and no chance to really start over because he's spent years fuming over petty revenge. If Lewis hadn't gone back in time, the poor guy's prospects would've been pretty bleak.
