From season 1 of The New Scooby-Doo Movies comes "The Phantom of the Country Music Hall", with actor-singer Jerry Reed as the guest of the week. Without so much as saying so, the Mystery Inc. team might as well be at the Grand Ole Opry in Nashville for this adventure. Reed sings "Pretty Mary Sunshine", which was originally recorded, I think, by Austin Roberts for season 2 of Scooby-Doo, Where Are You?, since the original version had a similar vocal as Roberts' faux-British accented cover of the theme song. Reed's version of "Pretty Mary" would later appear on the "Scooby's Snack Tracks" CD several years later.
Here's a sample, with "Pretty Mary Sunshine":
Reed fit the intra-network crossover pattern in that he had his own variety show some months prior, also on CBS.