I've got 3 in my HeartGold...it was a struggle to break all records of the Pokeathlon, because of Pennant Capture. Shiny Leaves weren't hard. It was just simply talking to your Pokemon that's following you at specific routes depending on nature. I'm aiming to obtain the other stars, through beating up 100 trainers in the Battle Tower. And obtaining (almost) all the Pokemon in the National Pokedex. And they're both hard!