I don't remember exactly where this slip-up occurs, but I know it's a scene at the fair, and it's easy to spot. You know Froggy's obnoxious voice? Well, I guess it must be done by computer because after Froggy says something, Spanky starts talking and he has Froggy's voice!
If you think about it, "Computerized special effects" - DIDN'T exsist in the 30's and 40's. And.......You have to keep in mind, any "slip-up", in any of the Little Rascals episodes, occured in an era that was just seeing T.V. for the first time. Any filming, or usage of special effects -like the "Froggy voice", were still being tested. I think the effects developers were just happy it worked.