I think the creepy one is Little Twelvetoes
Holy crap, isn’t that the one where the kid drowns? Man, I hadn’t thought of that one in a while.
“Little Twelvetoes” was actually my favorite, because of the whole base 12 concept. Also, I thought L12T’s look was based on Elton John; he could also play piano. 
A friend claims that when her high school government teacher asked her class if anyone knew the preamble to the Constitution about five kids started to sing.
In the tenth grade we were told to memorize and recite the preamble with the specific instructions of no singing.
The stuff still works: I got the DVD and my kids and I watch it a few times a year.
No one’s mentioned Rufus Xavier Sarsparilla? or You Know They’re Nouns?
The hit rate for these is amazingly high - only a few hit false notes.
It looks like Super Celcius wasn’t an “official” Schoolhouse Rock song, but was part of the same group’s The Metric Marvels short series. It was a PSA designed as part of the short-lived effort to urge the US to convert to the metric system.
3 Is The Magic Number by Elizabeth Mitchell (sample at amazon.com) makes me get something in my eye.