By skyforbes Adaptations inevitably make changes to the source material, either adding new elements or cutting out scenes or characters. Sometimes though, these changes create plot holes that weren't in the source material, either contradicting something that was already established, or omitting an explanation (which isn't necessarily a plot hole, but still very annoying).
For example, the Wizard of Oz infamously ends with Glinda the Good Witch telling Dorothy that she had the power to go back home all along with her Ruby Slippers. When asked why she didn't just say that from the start, she claims that Dorothy wouldn't have believed her, which is a rather questionable assertion. The original book has no such problem, there the Good Witch of the North and the Good Witch of the South are separate characters, the Good Witch of the North is the one that gave her the shoes, and Glinda the Good Witch of the South is the one to tell Dorothy how to go home at the end of the story.
So what other notable plot holes or weird leaps in logic weren't in the source material but were caused by adaptation changes?