This sounds an awful lot like Scary, from Big Robot, Little Robot, but I couldn't help it: THIS was the sound that I wanted. Oddly enough, when I first thought of this tune, I intended it to be the "j" track, but I realised it didn't sit right. Then, I realised that this tune was absolutely perfect for "d", and there you have it.
In terms of feel and mood, though, it's very far from Scary, which was goofy, slapstick and almost self-deprecating. This one, however, is merely a jumpy and neat little song intended to make the listener smile, at least a little bit. The "dark" second piece was mostly a facetious way to add some tension to the song, and hopefully the resolution from that hanging diminished chord into the sparkly coda in C major should show that it's not a menacing moment at all. This is, legimately, a happy tune.