Our many-generational response to the "I want, I want" from kids was always "People in hell want ice water, but that doesn't mean they're gonna get it"
A couple of my favs are "it's about as much use as a chocolate fireguard" and a reponse to me as a child when I asked for something unreasonable "Do you think its charity week".
For some reason a girl I used to work with used to say if it was hot "I'm sweating like a shepherd".