Recycling

Robin Hood, released in 1973, was made during a financially difficult time for Disney and the budget was much smaller than any of their previous films. To cope with the restricted budget they reused some of the animation from earlier Disney films. This montage shows how a dance scene was made out of recycled animation from Snow White & the Seven Dwarfs, Jungle Book and The Aristocats.

Disney// Recycled Animation

I'm surprised there aren't more directors of live action films using recycling techniques as a way of cutting costs. There are plenty of generic elements (blood spurts, muzzle flashes, crowds etc.) and CG models (vehicles, buildings etc.) that get reused by VFX houses across different films and I'm sure shots have been recycled on long running franchises (Harry Potter, Twilight et al) but the only non-franchise example I can think of is Michael Bay's Transformers 3 that used a couple of shots from his earlier film The Island.  In this case the recycling was justified as the material was used to supplement a chase scene that's shoot had been cut short when an on set accident had left an extra partly paralyzed.

It's a different story with sound of course, with many films using sounds from the same FX library or sounds that the Sound Designer/ Mixer has used before. Here's the most famous reused sound; the Wilhelm Scream, used in over 200 films often as an in-joke.

Wilhelm Scream Compilation