Peter's voice cracking in "Dough Re Mi" was partly to cover the fact that he couldn't sing well. When the Brady Bunch Kids performed onstage, Christopher Knight took the least vocal duties of all, and Knight admitted years later that he "couldn't carry a tune in a bucket".
The Five Monroes are a take on the Jackson Five.
Carol tells Greg she'll stop worrying about him when he is sixty. Florence Henderson passed away just before Barry Williams turned sixty-one.
The title is based on the musical scale as taught in school: "Do Re Mi Fa So La Te Do."
The plot revolves around Peter Brady's voice changing. But Christopher Knight's voice didn't noticeably change until the beginning of the fifth season a year and half later.