While this isn't strictly a Scooby-Doo fun fact, I thought it was interesting and wanted to share it. It's always bugged me that Thorn mentions she's "1/16 Wiccan on my mother's side," as religion is a belief system and not something related to your family heritage or body chemistry. Apparently, the reason for her comment is that just like Christianity, where you "drink" the blood of Christ, the spirit of Wicca is considered to be in the blood of true believers. However, if the person chose to change their religion, they would no longer have the spirit of Wicca in their bloods. In this case, the "blood" is considered a non-physical concept, like many people believe their souls are in Christianity and other religions. However, this wouldn't completely explain that she only has 1/16 Wiccan blood. One possible explanation that I discovered is that Thorn could be questioning whether she is a Wiccan or not, in which case it is occasionally said that you have a fraction of Wicca blood, because you are basing your beliefs off of what family members told you and are not fully committed to the religion yet. A bit of a stretch, I know, but it certainly could be one possible explanation.
So, to sum it up, Thorn's comment that has bugged a lot of us actually is a valid belief of Wicca, and not just something a lazy writer threw in. It's really cool that WB took the time to research Wicca for this movie!
~ WildwindVampire ~