This is the strip that introduces the "character" that made me (Dave) laugh like a maniac when writing the scripts - the ghost of Phil Plait. If you are not familiar, his bio is here. I was looking for a figure to serve as a guide for Sofia, the equivalent of a Jiminy Cricket. Somewhere the idea of the ghost of Phil Plait ("but I'm not dead") occurred to me and it made me laugh, so thus it became canon.
Dave's Pick for the week: For some reason I was not a fan of the Replacements during their heyday but I really enjoy Tommy Stinson's solo work since the band broke up. His new Bash and Pop album is my favorite of the year and we are running out of time to find something I like better.