This is in the whole scene where Ralphie beats up the kid with yellow eyes. Every time the camera backs out (when you can see the street), the sky looks different; sometimes it's sunny and other times it's cloudy.
Practical to Fix
How did this make it past the reviewers? One of the qualifications for a slip-up is that it's practical to fix. And I quote: "There are some things that are either impossible to fix, or totally impractical, and these can't really be considered Slip-Ups. For example, CLOUDS IN THE BACKGROUND are impossible to make continuous, if the scene has any edits at all...But anything that is reasonably fixable can be considered a Slip-Up."
Literally a textbook case of NOT A SLIP-UP!!!
It's a slip-up. How long could that scene have taken to film when the sky could possibly change from sunny to cloudy? They could have made it at least look like it was continuous.