|This needs a stretch. (Feel free to remove when satisfied of completion.)|
Needed: History is incomplete.
"Demented speaker" was a nickname used by Velma Dinkley for Danny Darrow when she only knew him as a voice on the radio. He used the radio to communicate with the new Mystery Incorporated while they were exploring the Darrow Mansion, and at one point even tried to pretend that he was a recording.
Scooby-Doo! Mystery Incorporated
Danny Darrow used it to communicate with the new Mystery Incorporated.