Most complicated evolution ever
Leveling up to 69 and 3/9ths, while surfing on a level 70 keldeo in it's resolution forme, in a sandstorm, using a dawn stone while the pokemon is holding a PPmax at 9:46pm after beating 30 Arceus Using only Magikarp
On a more serious note, How about some Mechanical evolution. I mentioned this on another thread.I'm thinking something similar to the scenario of Genesect. What if they include a Machine in some hidden/evacuated Laboratory which you can use to evolve certain Pokemons. Specifically Fossil pokemons.