Just a quick bit of information since it was requested elsewhere...
If you happen to be one of the more social pokemon trainers out there, chances are that while chatting with your favorite trainees, you have been surprised with a Shiny Leaf or two. These can only be seen on a pokemon's status screen and are not actual items intended for use. So, what is their purpose? Well, if you are looking for some sort of amazingly helpful item or reward, you will not find it here. The prize for this "side quest" is intended more for the completionists out there rather than the battlers. For those who locate five Shiny Leaves with a single pokemon, a star will be conferred upon their trainer card!
Here is how it works:
To find Shiny Leaves, one needs to be standing in a patch of grass with their partner pokemon. Upon talking with the pokemon, it will start with a red exclamation point, spin twice, jump twice, and then have a green musical note over it's head. Immediately following this dance, you will get a message that says...
"................Oh?
(Pokemon) is holding some kind of strange, Shiny Leaf...
(Trainer) found a Shiny Leaf!
(Trainer) put the Shiny Leaf on (Pokemon)!"
Unfortunately, these special leaves cannot be found in just any patch of grass. The leaf locations available to a specific pokemon are based upon it's nature. These locations are listed below in alphabetical order.
Natures..............
Locations
Adamant...........Routes 9, 15, 22, 24, 37, 42, 46
Bashful.............Routes 10, 16, 25, 27, 38, 43
Bold.................Routes 9, 15, 22, 24, 37, 42, 46
Brave...............Routes 9, 15, 22, 24, 37, 42, 46
Calm................Routes 2, 4, 6, 28, 32, 35, 48
Careful.............Routes 7, 8, 13, 14, 33, 36, 45
Docile...............Routes 7, 8, 13, 14, 33, 36, 45
Gentle..............Routes 2, 4, 6, 28, 32, 35, 48
Hardy...............Routes 9, 15, 22, 24, 37, 42, 46
Hasty...............Routes 11, 18, 26, 39, 44
Impish.............Routes 1, 3, 5, 12, 18, 31, 34, 47
Jolly.................Routes 1, 3, 5, 12, 18, 31, 34, 47
Lax..................Routes 2, 4, 6, 28, 32, 35, 48
Lonely..............Routes 10, 16, 25, 27, 38, 43
Mild..................Routes 11, 18, 26, 39, 44
Modest.............Routes 7, 8, 13, 14, 33, 36, 45
Naive...............Routes 1, 3, 5, 12, 18 31, 34, 47
Naughty...........Routes 1, 3, 5, 12, 18 31, 34, 47
Quiet................Routes 7, 8, 13, 14, 33, 36, 45
Quirky..............Routes 11, 18, 26, 39, 44
Rash................Routes 11, 18, 26, 39, 44
Relaxed............Routes 2, 4, 6, 28, 32, 35, 48
Sassy...............Routes 1, 3, 5, 12, 18, 31, 34, 47
Serious.............Routes 7, 8, 13, 14, 33, 36, 45
Timid................Routes 10, 16, 25, 27, 38, 43
As you can see, more than five possible routes are listed for most natures. Because of this, it is possible to search on a route and not find a Shiny Leaf. If you seem to be having trouble on one route, try others! Also, keep in mind that you will probably have to talk with your pokemon quite a few times before a leaf decides to turn up.
Once you have found five Shiny Leaves, take them to your counterpart (Lyra or Ethan), and they will turn the Shiny Leaves into a crown for your pokemon. Just like the leaves, this crown only shows up on the pokemon's status screen.
In addition, he/she will present you with an award that can be looked at by talking with them again.
Finally, you also get a brand new star on your Trainer Card. Good luck on your hunt!