This is basically the collection part of Feel the Magic. Like Advance Wars' medals and Sonic's Chaos Emeralds, in Feel the Magic you must complete the girl's wardrobe.
By finding the rabbits (see Extras, earning stars on Memories mode and completing Story mode you unlock more and more, which allows you customize your girl with tops, hats and shoes. Some of these are normal but others include Santa Claus, nurses, and policewoman's outfits.
You can also collect special SEGA outfits by entering GBA carts into your DS whilst playing Feel the Magic. For more on this see Extras.
There are a total of 21 hats, 21 outfits and 13 shoes to collect.