I am running a fairly basic Pokemon team and my first EV trained one at that. And I am in the Battle Tower to test it out with a prankster Whimsicott with leech seed and I am against a Mandibuzz and a Crawdaunt. I use leech seed on Mandibuzz and apparently it doesn't affect it? Please help as I am very confused. :)
As of Sun/Moon, all dark types are immune to moves boosted by Prankster.
Dark Type Pokémon are immune to Prankster moves like Leech Seed since Gen. 7.