This post is another in an ongoing series where the sole point of the post is to make it easier for me to find this information in the future—instead of searching sites and finding tons of wrong answers, I can just search my blog and find the right answer. If it's useful to anyone else, that's a bonus.
Sometimes, I want to reverse a video, usually for humorous effect—to turn a disassembly time lapse video into an assembly time lapse video, for example. If you have ffmpeg installed (via Homebrew or MacPorts or other method), then it's quite simple to do. Here's the command:
ffmpeg -i original_movie.mp4 -vf reverse -af areverse new_reverse_movie.mp4
It doesn't have to be an mp4, of course—any format that ffmpeg can deal with will work fine.
(I originally found this solution on StackExchange.)