Plagiarism has become a huge issue in today society. There was a lawsuit against Youtube channel H3H3 Productions. They used parts of someone’s video and made a reaction video of those little clips. H3H3 won the lawsuit claiming fair use. They only had small clips and not he whole video used in their video. The main video was of them reacting to the video. They won their lawsuit.
Here is a link to help you understand the difference between plagiarism and fair use.