How did Facebook create the Friends Day video?

It’s a script that takes random photos of you and close friends profile picture and put them in the template you saw. If you requested it, you will notice that it takes time to render but the video size is low so it won’t take much time. And you can even edit it by yourself.

 

Source: quora.com

How to create custom profile frames on Facebook

Facebook Celebrates 15th Birthday With ‘Friends Day’ Video – 2019