The Bradys have a chalkboard in the kitchen. In the “Law & Disorder” episode, it says “Tuna sandwich” on it. What could this possibly mean? Perhaps it’s what is going into the Brady lunch bags tomorrow, but wouldn’t it say “Tuna sandwiches” instead? Perhaps Alice is writing down what she’ll be eating for dinner in the kitchen that night while the rest of the family eats in the dining area.

Are there any other episodes with mysterious messages on the chalkboard?

Probably and we just didnt ever notice...

The "Tuna sandwich" might have been for Alice yes...

Any shows where they were actually writing on it?

Little bit of trivia. You will notice that this chalkboard comes and goes. Its there in some episodes and disappears in others. There is at least one episode that its in another location too. It appears on the wall adjacent to the wooden swinging doors in the kitchen.