I visited the Planet Snoopy page on the visitkingsisland.com website. For those who haven't been there yet, there's an embedded slide show with what I believe to be the Peanuts theme, but not. Is it me, or is the song playing backward, or perhaps was someone playing the sheet music upside-down?

That music selection is a 'variation on a theme'... You can pick up on certain phrases that seem to be borrowed from the original Linus and Lucy by Vince Guaraldi

Some artists have released their variation on L&L, Wikipedia has a good listing of some of them...

http://en.wikipedia.org/wiki/Linus_and_Lucy

I remember learning to play this in its original key back in 4th grade and thought that I had really arrived as a musician, thank goodness there were other milestones after that!