Super Smash Bros. Lawl How to Make

[Asriel Dreemurr]

OK. This YouTube channel called YTPguy17 puts out amazing videos with fake Super Smash Bros. characters like SpongeBob and Bill Nye the Science Guy. He presents it in a family-friendly and often hilarious way. I have iMovie, but I need the animation program that he uses to post his videos. Or preferably, a free equivalent. Jellyfishbaby's views would rocket up if I got my hands on this. Can anyone please identify this program or a free equivalent?

Here's a video:

https://www.youtube.com/watch?v=JG7DNAT610g