Some people make up animation history. They come up with a conclusion and state it as “fact.”
A good example is the “fact” that animation backgrounds were redrawn at Warner Bros. to change dates on them (such as magazine covers in one short) so a cartoon wouldn’t look “old” to the audience. This odd claim has never been substantiated and, to be honest, I can’t picture anyone years ago sitting through a re-released cartoon in a theatre to either notice or care. To me, it’s just a weak gag, like when you see a wall calendar in a cartoon that reads “September 32nd.”
Here’s one such calendar in a long school house interior in Porky Pig’s painful debut “I Haven’t Got a Hat,” released in 1935. There’s a calendar on the wall which, if you blow it up and look close enough, reads either “1943” or “1949.” This is from the original cartoon with original titles, not some Blue Ribbon re-release from the ‘40s. So it obviously wasn’t altered. It’s just the anonymous background artist doing something silly, just like the lame joke that the map shows the country of “Mehico.”
Incidentally, if you’re wondering about the book on the teacher’s desk, it’s entitled “History of Kansas.” The fine, but abandoned, web site Looney Tunes Hidden Gags goes into detail about how the backgrounds around this time featured inside jokes about Tubby Millar and his hometown of Portis, Kansas. I suspect this is another one of them.