I found a commercial for Post Raisin Bran that is in color and appears to be from the 1960's/70's and features live action raisins. The commercial starts with a bowl of raisin bran set to some music and the raisins pop out of the bowl and start singing a song about Post Raisin Bran and then the commercial ends with the slogan "Post the more Raisin Brand"
Do you remember this commercial?
Bestie