The Finnish National Opera staged the Moomin Opera in 1974/75. The initiative came from the composer Ilkka Kuusisto. He had seen previous Moomin stage plays and contacted Tove Jansson about a possible collaboration, and only shortly afterwards Tove started writing a libretto. The story of the Moomin opera was the same as the stage play Troll i kulisserna written in a opera format. In the opera, however, the whole Moomin family was present.

In the Moomin opera an underwater volcano causes a flood in the Moominvalley, forcing the Moomin family to flee and eventually find shelter at the opera. Here the family starts pursuing the art of the opera. It turns out that the Fillyjonks housemaid Misabel is a real opera star.

The opera was musically very versatile and Ilkka Kuusisto made in addition to the classical children’s opera also oratorio songs, operetts and even electronic dance music. The Moomin opera was directed and choreographed by Heikki Värtsi, and aired for the first time in December 1974. The critics were not fully convinced, but the children loved seeing the characters live on stage. The opera was shown 34 times, and around 15,000 people got to see it.