Halloween 5's missing doctor death scene fixes major plot hole
Halloween 5: The Revenge of Michael Myers dropped the original opening scene, which ended up creating some plot holes in the final product.

The previously lost original opening scene of Halloween 5: Michael Myers' Revenge fixes some plot holes. Halloween 5 was quickly greenlit for the success of the fourth film, and production was rushed into production for its 1989 release. It started filming without a solid story, and that's evident in the somewhat messy final product. Halloween 5 kicks off with Michael Myers/The Shape narrowly escaped being killed by a vengeful mob, and a well-meaning hermit takes care of him for a year; of course, when Halloween returns, the hermit is murdered. The scene was re-shot and originally opened with a young occultist known as "Dr. Death."
He takes Michael into his hut, places him on a stone altar, and puts the thorns rune symbol on his wrist, bringing him back to life. Producer Moustapha Akkad thought the Dark Arts-themed scene was a bit silly and ordered a reshoot with an older character. This scene was lost for decades, but when it was finally discovered, it was included as a bonus feature on the Shout Factory 5 Blu-ray in 2021.
Halloween 5's Original Opening Makes More Sense

This scene builds the story better, explaining where Where did Michael's thorns tattoo come from and why he hasn't played in a year. A big legacy of Halloween 5 is the introduction of the Men in Black. The character dresses up like a cowboy, has a prickly rune tattoo, and frees Michael from prison in the finale. The character wasn't originally part of the script, but was added during filming to piece together loose narrative threads. Akkad also felt that the movie needed an extra hook for another movie, so it became unclear who the man in black was.
HALLOWEEN: The Curse of Michael Myers attempts to resolve the unresolved issues of Part 5. It is revealed that the Cult of Thorns is controlling Michael, and that the power of the runes grants him special powers and drives him to murder his bloodline. This reveal is one of the most maligned storylines in the entire Halloween movie franchise, and was retconned in Halloween H20. The deletion of Halloween 5's Dr. Death opening had some knock-on effects on the narrative, though it wouldn't necessarily make the sequel better if it had been kept.
Halloween 5's Other Major Deleted Scene Is Still Lost

Halloween 5 also had several revisions to the violence, including Michael's moment Stabbed Jamie in the leg as he climbed up the laundry chute. Another famous deleted scene that has yet to be discovered involves Michael slaughtering an entire SWAT team waiting to ambush him. This is before the final showdown at the Myers house, where Michael uses creative methods to take out his enemies, like using the barrel of an M-16 as a spear. The entire carnage happened offscreen in Halloween 5 - which almost redeemed Michael - and while fans hoped it would be discovered along with the Dr. Death sequence, it still seems to be lost.