Got £1.19 to spare?
Operatically-themed apps are thin on the ground. And I'm pretty certain Battle of Puppets, launched yesterday, is the first opera game.
It's basically a castle battle between two opera armies - you can choose from Carmen, Aida, Madam Butterfly, Valkyrie and Salome. The sweet little units are all naked except for their operatically-themed headgear (was it directed by David McVicar?) The action is set in various US cities, and the battlefields are stages with moving scenery. It's all very cute and charming and retro, and if the gameplay isn't very sophisticated, what do you expect for the price of a bag of peanuts?
There's a detailed review on toucharcade.com, and here's a video: