In v1.3.4, adoptables are created in five places - adopt.php, admincp/ownedadopt.php, classes/class_breeding.php, classes/class_promocode.php and classes/class_stockadopt.php. You'll want to add stats in all these places.
Otherwise, everyone should be sure to reference
this post from a few up (in it, the post numbers are links to the original versions of posts). I installed on v1.3.4 and really the only thing that changed were line numbers. It's better to search for exact contents than rely on line numbers!!
Oh, and in addition to just number stats, you can also give a pet a random personality, for example --
PHP Code:
$personality_array = array('brave','honest','loyal');
shuffle($personality_array);
$personality = $personality[0];
A reminder that when adding this mod, be sure to add a default value while creating a column, that way any existing pets will have that value. It won't be random, but hey, they'll have something.