Weird references in vintage cartoons

[Peter_Morris]

I asked the same question in 2008.
There are at least two other cartoons using the same joke, including a Bugs Bunny, and another Tom And Jerry.

- YouTube

Origin of quote - don't you believe it

Does anyone know the origin of this quote, the words “d-o-n-'t y-o-u b-e-l-i-e-v-e i-t” in a deep booming voice. Used in a few cartoons: Mouse Trouble(1944) Big Top Bunny (1951) The Missing Mouse (1953) I get the impression that it’s a reference to some movie or radio show that would be familiar to audiences in the forties and fifties. Anyone know what it is?