Unlike several other similar phrases, this one is actually effective, because I simply refuse to accept any garbage the children hand me. I say, "I am not a garbage can!" and point them in the direction of one. Works every time.
As I tell my girls, I don't speak Whinese. You know, it's what they speak in Whina, right near China. I can't imagine how my kids picked it up, never having even been on a plane, but they must just have an ear for languages.