Where Do I go For Extra Pet Space!

You can buy extra pet slots from the Millionaire Center starting at 20m sP for the first slot (25 slots max) or for 1500 CSC each on the Pets page (65 slots max)

Starting on your 2nd site anniversary, you get a Loyalty Box every year where you can get a free pet slot, and if you participate in the currently running Quest-a-thon event, you'll also get a pet slot when it ends