To get the special iD L characters, you will need to raise four characters with all their happy symbols. Then you will unlock a destination called the Heshin Jo. Then you will need a certain TamaMori item , Download item , Gotchi points or a toy.
King Kikitchi - 3000 Gotchi
Metal Kuromametchi - Metal Guitar
Prince Mametchi - Crown
Musha Gozarutchi - Download
Patchizaura - Download
Jigoku Queen (Makiko) - Download
Devil Memetchi - Download
Hapi Chamatchi - Wing Hat
Reporepo Uwasatchi - Microphone
Tamamoriritchi - Kiramori Schrunchy
Majokko Furawa - Download
Melodi Hime - Kimono
Princess Lavuli - Princess Dress
(thank you binary for the info)
(EDIT: Sorry. Me and binary must be posting at the same time
)