What is the difference between a bobble, a popcorn and a puff stitch?

Yarn over, insert, pull up a loop, yarn over, pull through two — that is one incomplete dc. Work three to five of those into the same stitch, then yarn over once and pull through all remaining loops. One loop is left on the hook, so the bobble occupies exactly one stitch position.

A 4-dc bobble in worsted weight stands about 8 mm off the fabric and is dense enough that light does not come through it. That makes it the right choice for eyes and noses on amigurumi, where a popcorn would be too rigid and too hollow underneath.

Work five complete dc into the same stitch, drop the loop off the hook, insert the hook into the top of the first dc, pick the dropped loop back up and pull it through. That fans the five stitches into a rounded clump standing about 12 mm proud.

Popcorn reads larger and flatter-topped than a bobble of the same stitch count, and it pulls in the fabric around it harder. In a blanket it creates a raised grid; in a hat it can pull the crown off-round if it sits too close to a decrease.

Yarn over, insert, pull up a loop to the height of a dc; repeat four or five times into the same stitch without closing any of them. You now have 9-11 loops on the hook. Yarn over and pull through all of them at once, then chain 1 to lock it.

A puff is the softest of the three and the only one that squashes flat under a finger. That is why it suits baby blankets and washcloths, and why it makes a poor eye on a toy.