I was just listening to the Dennis Day Show episode of March 26th, 1947.
This was just a week-and-a-half after Bing Crosby inadvertently ad libbed "Who the hell picked out this key, Dennis Day??" on Jack's show.
In the opening song, Managua Nicaragua, Dennis speaks: "Who picked out this key, a baritone?"
I found it especially interesting because the policy of the era seemed to be "ignore the fact that anything happened, and don't even refer to it," when something slipped out like that.