Aside from Elmer Fudd singing "Kill da Wabbit, Kill da Wabbit!" I'm a newbie on opera, but............
Stumbled on a 2-CD gala performance of Die Fledermaus on Decca that sounds FANTASTIC! Tremendous clarity, yet non-fatiguing. The notes suggest parts (all?) of it were recorded in 1960! The second disc has songs by Lehar, Loewe, Irving Berlin and Gershwin (WTF?), but regardless, it all sounds wonderful. Highly recommended!