Non-English speaking vocalists singing in English (especially Brazilians). Sing in your own language. I like the mystery of being clueless about what you are saying.
Even if they're making fun of all the stiff upper lips in the audience?
Can't understand them so they can be singing about what they like. Actually, it tends to be worse when the translate lyrics from the native language into English!
I'm sure Stacey Kent singing in French sounds awful to the French.
They probably like it - after all, a previous generation liked Petula Clark singing in heavily-accented French.