For images, any reverse image search program such as TinEye, Google, Bing, or Yandex. I find sometimes they give different results and that TinEye often has not indexed the images I search even if Google has.
Unfortunately videos don’t have an easy reverse search. You could try taking a screenshot of a video frame and image searching it, but it’s likely to not come up with anything.
Somewhat unrelated to your use case but Saucenao and IQDB are great resources for finding original anime images.