I was looking for something to make for ferrets and found references to egg toys. The instructions I found said to put unpopped popcorn into a child's plastic easter egg, tape it closed and crochet around it with acrylic yarn. I didn't want to use organic material that might mold and I didn't like the idea of using tape or the acrylic yarn. Ferrets can easily get intestinal blockages and if they ingest tape or acrylic yarn I'm sure that could cause a nasty one.
I decided to use cheap plastic beads for the rattle, my favorite are the "snowflake" beads that were popular in the 1970's. I found some size 3 cotton thread in my stash and crocheted tightly around the egg to keep the pieces together instead of using tape. Because I didn't use any organic material they can go in the washer with the ferret bedding and they air dry pretty quickly.
I gave the first ones I made to my ferrets to test them out. I also gave some to the shelter where we adopted 3 of our 4 ferrets. The shelter moms love them because they are safe for the ferrets and they wash up easily. The ferrets like them because they make noise and even the smallest can get a grip on the egg to carry it off.
I didn't really use a pattern for these because the plastic eggs are all different sizes. If you can crochet in the round, and increase and decrease you can make these toys.