The "silence in my kitchen" mantra came from Fred's sons making a lot of noise and disturbing their Mom while she was preparing food in the kitchen. Fred figured that this must be a problem in many households, so he created Chef Brockett to emphasize this concept of being quiet in the kitchen. It worked. Mr. Rogers acknowledged in at least a couple episodes that parents have told him that kids stay quiet in the kitchen. In later episodes, Chef Brockett doesn't insist on silence as much, but I guess Fred figured he got the point across enough, and besides, it's still not incredibly loud in Brockett's kitchen.
