On October 30, 1968, there was a TV Musicians strike against the 3 major networks: ABC, CBS & NBC. In this, and other episodes, you will see improvising with sound effects and vocals.
The usual live band is absent for this episode. Carol sings a loose, ad lib version of the theme song instead of the usual orchestral arrangement, and cast members sing the "bumper music" between and introducing sketches. At show's end, she races through a half-spoken/half-sung version of her usual closing song, over a slow, choral recording that plays on through the credits.