Kellogg's Rice Krispies
In the early days of television, a show couldn't get on the air if there was no sponsor signed on. The advertiser, alone or in partnership with the network, paid the cost of production in exchange for commercials and product plugs throughout the program.
The practice of using sitcom characters as salespeople disappeared almost entirely in the seventies. Television stars were now big enough to command their own endorsement deals and didn't want to be landed with network commitments into which they had no input.
One of the last network/program sponsorships was Kellogg's sponsorship of The Partridge Family in 1970. The first commercial shows the whole family waking up to the sound of Kellogg's Rice Krispies.
In the second commercial there was no close-up of Laurie Partridge, played by Susan Dey because she had a separate deal with Misty hair dryers.
In another commercial break for Rice Krispies, only Shirley Jones and David Cassidy are seen. The jingle is sung by The Partridge Family (the regular recording singers, Shirley Jones and David).