the characters are extremely well written
they have personalities, wit, are likeable.
as a not young viewer, i appreciate the attention & care the creators put into doing this thing right.
for a sci-fi adventure show, this is pretty high Q stuff.
working through season 3, its still holding together very well. i especially like 'trev's' character, the world-weary old fellow in the teenagers body, and the nerdy chinese guidance counselor / quantum physics nerd lady who is trying desperately to jump his bones.