The Mickey Mouse Club featured different theme days. Monday was "Fun With Music Day" which typically featured a day of music and songs sung by the Mouseketeers themselves.
Mondays were a day when the Mouseketeers could show their musical talents by singing and dancing. Originally conceived as a showcase for Darlene Gillespie, who was seen as being the "star" of the Mouseketeers, it quickly became a day for Annette, who had been crowned the star by the Mouseketeers at home.