A really powerful activity is to share video clips* with students not just for them to view, but for them to download onto their own device to edit, remix, trim, and integrate with their own media to make a movie of their own. The workflow is a little different if you're using laptops or iPads:
On laptops this is very easy, if you upload the video to Seesaw they can just choose download from the '3 dot menu', or right click on the video and download. Or— easier to share across a team, link to a video in Google Photos or Google Drive for them to access and download.
For students to be able to download videos on an iPad you have to upload the video into Seesaw, you can use a link to a video. Once you've uploaded the video to Seesaw, the students can open it and use the share icon to save the video to their camera roll.
*where can you get these video clips? Well one way is to just download them from YouTube, there are several ways, more on how to do that here. But remember, as is always the case with video, avoid using videos that are looooong, and/or really high resolution, otherwise the downloading process can take a long time.