The creepy voice is an unknown entity that was only seen as a blue light.
Scooby-Doo! Mystery Incorporated
The doorbell rang at Sheriff Bronson Stone's office. When he answered it, a blue light showed from it, and a deep voice said "OH SUCH SIGHTS!" Only for Sheriff Stone to close the door and say, "Weirdo."
- The voice manifests after Stone plays with a puzzle box from the Traveling Cabinet of Curiosities. It clicks open and rearranges in a manner very similar to the Lemarchand's box in the Hellraiser movies. The creepy entity may be meant as a parody of a Cenobite from those movies. The quote, "OH SUCH SIGHTS!" is like "We have such sights to show you!".