Porky Pig - That's All, Folks! 

That’s all folks

Yes. That also was the ending of the opening, where he said, "That's me folks!", then stuttering into "Brought to you by..." and then the sponsor film would roll. I think there was then a closing credit for Warner Bros. and ABC.

I see that at the very end, Porky was reopening the circle. Was he going to announce the sponsor?