The Flintstones' original run ended in 1966 and their popularity with prime-time audiences caught the eye of executives of Anheuser-Busch.
Hanna-Barbera was contacted to produced a complete 23 minute episode of The Flintstones entitled "Busch Advertising 1967".http://www.milkandcookies.com/link/68368/detail/
The film was not intended for public broadcast but for Busch beer distributors to inform them about Anheuser-Busch's advertising campaign for 1967.
The Flintstones had already advertised Winston cigarettes so Busch beer was no surprise. Times sure have changed.