A must when jointing children's toys.  These 25mm plastic joints come in 3 parts:   stem, washer and locking nut (or washer)

Please note that they do require some pushing (and strength  : ) to fit correctly.   Once on, they cannot  be removed !

Sold singly, ideal for getting that softie's head to turn  -   I recommend sewing limbs into place for younger children (much softer to hug  : )