The third unit headed by Mike Lah and Preston Blair was disbanded and Metro, for a time, distributed cartoons made by John Sutherland Productions. The Tex Avery unit was shut down in 1953. And the Hanna-Barbera unit pinched pennies by finding ways of reusing animation.
Here’s an example from Cruise Cat, released in 1951. Tom pursues Jerry into a movie theatre on a ship. They stop.
The camera pans right to left over one of Bob Gentle’s backgrounds and stops at the movie screen. It’s showing Texas Tom, made in 1950.





Sorry, the shot moves not only across, but down the background so I can’t put the frames together. Tom and Jerry settle in to watch their cartoon.

The film then uses footage from the old cartoon from 4:43 to 5:11 before cutting to new reaction animation of Tom and Jerry by Ken Muse.

From 5:15 to 5:36, it’s back to the re-used footage before cutting back to new animation for the rest of the cartoon.

Hanna and Barbera found different ways to incorporate footage from previous cartoons in cartoons such as Jerry’s Diary (1949), Life With Tom (1952) and Smarty Cat (1954—a Daws Butler cat shows “home movies”). Of course, other studios did the same thing.
Finally, MGM found a way to save lots of money on cartoons. It stopped making them. Hanna and Barbera moved on to a new project in 1957, but that’s a story for another blog.