Frankenstein Meets The Wolf Man (lost scenes of Universal horror film; 1943)
Frankenstein Meets the Wolf Man is a 1943 horror film depicting Frankenstein's monster confrontation with the Wolf Man. It's known as the first of Universal's crossover monster films but was met with mixed reviews (currently holding a 25% on RottenTomatoes). It is also notorious for its deleted and lost content.
As well as the lost Bela Lugosi dialogue audio, there were several shot scenes that didn't make the final cut. In the 1980s, searches through Universal's vault for an uncut prerelease version of the film started, but the scenes have still not been recovered.