Lay your robe out and design where you're going to place the stuffed animals. I don't recommend too many on the back if you're going to be doing a lot of sitting.
Attach the stuffed animals in one of two ways - either using the needle and thread (if you'd like to reuse the robe) or with the hot glue gun and sticks. I used one glue stick per cat.
Notes
You can greatly reduce the cost of this costume by shopping for your robe and stuffed animals at the thrift store! Just be sure to give yourself enough time to find plenty of cats.