Sadly I only watched four movies, the first 3 and then one of the last ones where they basically did a remake of the first season. I choose you I think it was. So I have no idea about Genesect.

But what are the more playful legends? Could the Lake Trio swarm around his head and taunt him? 

Or maybe Meloetta, who may be secretly rooting for Gavin to find a partner, be it another Legendary Pokémon, a regular Pokémon, or even a human. Meloetta isn't shy amongst humans, according to the Bulbapedia she lived in a village with people, so she might even appear to them in her Pokémom form. Which will also allow Mindy to see something the others haven't.