Daphne Blake is a "mystery hunter" and a member of the Scooby Gang, along with Scooby-Doo, Shaggy Rogers, Velma Dinkley, and her boyfriend, Fred Jones on the TV show Scooby-Doo, Where Are You! as well as multiple other TV and movie variations. She then appeared in the official Scooby-Doo, Where Are You!/Supernatural crossover episode in season 13, titled Scoobynatural.
In Playthings, Sam and Dean go on a ghost hunt to a Victorian mansion. Dean states that they never get to check out classic haunted houses, and says they might even run into Fred and Daphne while inside. He then expresses interest in Daphne.
In Form and Void, Crowley and Dean are searching Jenna Nickerson's house for Jenna and baby Amara, and Dean yells for Jenna. Crowley then warns him that they are basically telling Amara that they are coming, to which Dean replies by calling him Velma and that they aren't the Scooby gang, so he needs to shut up or leave. Crowley retorts by saying he's "way more of a Daphne."
In Scoobynatural, Dean and Sam are given a brand-new TV. When the TV starts to act odd, sending Sam, Dean, and Castiel into the Scooby-Doo, Where Are You! episode "A Night of Fright Is No Delight" where they team up with Daphne, Fred Jones, Scooby-Doo, Shaggy Rogers, and Velma Dinkley to solve a mystery. While Sam and Castiel want to use them to escape, Dean wants to keep them "pure." Dean attempts to woo Daphne away from Fred, to no avail.