Trail of The Pink Panther (1982) Made well after Peter Sellers death, there’s a bunch of unused footage of him from the previous PP films.

Ewoks:The Battle For Endor (1985) Unused footage from ROTJ appears in the final battle scenes.

Revenge Of The Sith Teaser -Alternate take/angle of Alec Guinness talking about Vader from the original Star Wars is used.

Magical Mystery Tour (1967 The Beatles) It’s alleged unused aerial footage from Dr. Strangelove was used in the Flying sequence. (Much to the ire of Stanley Kubrick.) The black and white footage was colored, (not to be confused with colorization) making it resemble part of the stargate sequence in 2001 A Space Odyssey, which came out the very next year.