Fenrir's Fangs

In this case I would say fusion dance. Besides if it were a potara fusion that move would become useless and you would just delete it to make room for fly. XD

However I had an idea when I was younger to make a pokemon game where you could fuse any pokemon with eachother and it makes a new better one. I also decided to make it more difficult where to fuse them you had to have two halves of a fusion stone and give each of the two chosen pokemon one of the halves and then a fusion would take place and it would be permanent. Infinite possibilities......