Met the Robinsons. They're an oddball family who exist sometime in the future. Each family member has his or her own eccentricities, but they accept each other with mutual love and respect regardless. Such eccentricities include minor dementia, schizophrenia, belief in the anthropomorphism of amphibians, delusions of grandeur, extreme sibling rivalry, and psychomotor disability. Exhibiting any one of there traits could land an individual in an institution, but collectively united by blood and heart they pull together as the Ideal Family.
In fact, the only trait that poses any danger to anyone is typical teenage irresponsibility, and even then, Wilbur Robinson does his best to rectify the grave error he has committed.
The Robinsons are quirky enough to extend an invitation to orphan boy, Lewis, to join the family despite having their house nearly wrecked by a rampaging tyrannasaur as a result of his arrival (take it as it is, it's too complicated to explain). But when they discover that Lewis is from the past, they freak out and withdraw their invitation, insisting that he return to his own time.
The movie deals with the themes of failure and rejection. The Robinsons themselves celebrate failure -- the more spectacular, the greater the rejoicing. Or rather, they celebrate the learning that failure brings, while downplaying success which doesn't teach a whole lot. Hence the Robinson motto: Keep moving forward.
Lewis is himself a bright young man who has many great ideas, but his inventions often fail in their execution. He also has to face rejection several times over as his imagination and his devotion to science fail to endear him to the prospective foster parents who come to the orphanage to interview him. Apart from Mildred who looks after him in the orphanage, the Robinsons actually offer Lewis a home and a family, so it's especially heartwrenching when they eventually reject him too. But they have a good reason to send him back to their past.
The future is both predestined, yet it isn't set in stone. The choices we make in the present set a chain of events in motion that lead to the future. Conversely, the future depends on the choices we make in the present. The critical choice in this movie is Lewis's. One thoughtless incident is all it takes to change the idyllic utopian future into a horrific nightmarish one. He has to learn what that moment is, and make the right choice or end up irrevocably destroying the Robinson family of the future.
The plot sounds quite serious, but the comic relief comes in the form of the Bowler Hat Guy, arguably one of the worst evil villains to ever take up a career as an evil villain. He is the result of living a life of failure, yet never learning anything from his experience. His evil plans fail because he seriously lacks vision, knowledge and follow through. He is pure impulse who has unspecific goals, and no idea how to achieve them. It's hilarious when his plans fail. He deserves to fail because he doesn't think ahead or learn from his past mistakes. Resilient and persistent but neither resourceful or innovative, BHG is just pathetic.
Lewis, on the other hand, is driven by his desire to find his birth-mother. He studies through the night, attends university lectures uninvited -- and still dares to question the lecturer for more information -- and applies his learning to create a device that will help him achieve his goal. All he needs is encouragement and a realization that his many failures are necessary stepping stones towards the success that has so far eluded him. The bigger the goal, the more steps it takes. Lewis we root for, and hope that he will eventually find the belonging he so desires.