Kiri Te Kanawa was the lead in the production of Die Fledermaus I watched. That was also one of the most fun ones so far. Mostly German, a mixed-in bit of English, with Te Kanawa providing occasional commentary in English from the stage. As she's meeting the initial parade of male characters, she's introducing each one and what they do. As #4 comes on — I think it was Falke — she does her usual introduction, then sits down in a heap and says "At least he's not another tenor.". There were many small moments like that, including Domingo's call from the pit and Frosch's call-out on stage.

I watched a production of The Marriage of Figaro yesterday, and have The Barber of Seville on the list (thanks, Looney Tunes!). I will look for more Kiri Te Kanawa work; thanks for that suggestion. And I'll mix in your opera suggestions as well.