Many of the toys I’ve knitted involve sewing down to the cast on edge, where you are then told to pass the yarn through the cast on stitches to create a drawstring effect. I did this several times and found the results less than pleasing. Now, if the pattern includes this process, I start with a longer yarn tail when casting on. Once I have all the stitches cast on, I thread the yarn onto a darning/tapestry needle and thread it through the stitches before going on to the first row. When that part of the project is completed, I have a drawstring already in place for the cast on stitches edge! You do have to be a little bit more careful doing the first row, avoiding splitting or picking up the threaded yarn, but it works so much better.