@draugluin, so what I'm getting (from looking at that briefly) is that it allows you to assign your pet to a group via that pet's manage page? That is very handy!
EDIT:
Made some fixes to it so that it works properly, just replace the database update line with;
PHP Code:
$mysidia->db->update("owned_adoptables", array("pet_group" => $wahl), "aid ='{$adopt->getAdoptID()} ' and owner='{$mysidia->user->username}'");