Very well crafted. I think it scratches the same itch as Adventure Time -- surreal fairy tale -- while changing the tone just a little bit to be more grim (or even grimm), more adult, darker, more folksy. The plot is pretty meaty, the episode-to-episode designs and themes are great. Elijah Wood's performance is very good, as it usually is, playing a nervous sad sack. Colin Dean as Greg is phenomenal, and brings that great kind of orthogonal thinking madness that enthusiastic children always have. The running gag with the frog's name is wonderful. And the way new characters stick around for an episode or two is great, a real "merry band of brothers adventuring" feel. Very cohesive as well. The singing and musical elements are great too, because they're not too catchy and just creepy-weird enough for the whole thing to have a vaguely unsettling tone. Really really great achievement.
I'm not sure if CN is planning on doing another season, but the people involved should be very proud and I hope they get the opportunity to tell other stories later.
There's very little chance this won't make my top 10 this year.
How do you feel about Simon Universe?