This piece about a batch of Warner Bros. animated shorts for the war department that would be owned by the Feds if they had only renewed copyright is worth perusing.
... it’s fairly startling that any of the Private Snafu cartoons ever got made. All of the cartoons required War Department approval before they were screened, and no one ever accused the U.S. military of having a sense of humor. But the films place a very heavy emphasis on slapstick knockabout, often using slightly blue jokes, mild cussing (the word “hell” turns up) and vaguely tasteless gags to get their points across. But somehow or other, the cartoons received official approval, resulting in 28 shorts (averaging slightly less than five minutes) that were made between 1943 and 1945.
You can go through the $2 DVD bins at Toys-R-Us and other places and come across Public Domain Fleischers, Warners and Schlesigner cartoons (and a few others) that never got their copyrights renewed. (This never happened to the Disney product, for Uncle Walt wasn't that inattentive.)
It would be pleasant indeed if somebody could pin down negatives and/or first-generation prints for a lot of this material, since a lot of it is worth owning if it's not a dupe of a dupe.
Otherwise, not so much.