It's astonishing how quickly Psychonauts sketches out its world. Two hours in and I completely buy into it. Not because it is particularly plausible or detailed, but because it so clearly has its own voice that it can't possibly be mistaken for anything else. I believe I said something similar about Broken Age, but it feels like one of the higher-quality offbeat children's cartoons (but, like, a different offbeat cartoon than the one in the other game).
I think it's a useful contrast to have played this game back to back with Two Worlds. Not to knock Two Worlds (which has probably already suffered enough), but the difference between the games makes abundantly clear the difference between great video game writing and not-so-great video game writing. The script efficiently communicates the stakes of the conflict and roots those stakes in well-thought-out character motivations. Even if you couldn't see the screen, it would be obvious who's talking, both from the great voice-work and because the dialogue manages to convey more than just factual exposition. The way characters express themselves is part of their overall design. And if they are little more than shallow types (as keeping with the game's overall "kids' cartoon" aesthetic), then at least they are well drawn shallow types, who can pack a surprising amount of information into something as simple as a hairstyle or a turn of phrase.
The most illustrative example is the difference between Two Worlds' Gandohar and Psychonauts' Sasha Nein. Both are mysterious ciphers who are nominally on the hero's side, but possibly possess a sinister hidden agenda, but in Two Worlds this is built up by the protagonist and his sister Kira repeatedly asking each other variations on "Should we trust Gandohar, he seems to want to help us, but what is his real agenda?" Whereas in Psychonauts, Sasha Nein establishes his mysterious antihero cred merely by hanging around in the background of more positive scenes, baiting the hero with obvious half-truths, and living in the basement of a cluster of spiky geodesic domes that are the psychic equivalent of a prison hotbox.
It is this clarity of vision, combined with the occasional laugh-out-loud quip or gag, that makes Psychonauts such a joy to play. It's self-consciously weird, but not overly precious, and I can't wait to see what happens next, nor to learn more about this quirky cast of misfits.
Oh, and the platforming is pretty good, I guess.