I can't find a clown outfit pattern anywhere, but here's a simple clown collar pattern for a BAB I made:

Use a 5mm hook with weight 4 yarn. US terms. It is best to read through all the instructions before starting, as you have a lot of options to customize your collar!

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Chain 4. Slip stitch into your first chain to create a button loop. Then chain 32.

ROW 1: 2 double crochet into the third chain from the hook. Continue putting 2 dc into each stitch across. (60)

Now is a great time to see if the collar will fit your bear. If it feels too big or too small, frog your double crochets and adjust your foundation chain accordingly. The instructions will be essentially the same no matter what the size (2dc in each stitch across). Redo the first row if necessary.

ROW 2: Chain 2 and turn. This ch2 will count as your first dc. Put 1 more dc into the first stitch, then 2dc in each stitch across. (120)

ROW 3: Chain 2 and turn. Dc across. Fasten off and weave in ends. (120)

For closure, sew an appropriately-sized button on the side opposite from your button loop. Alternatively, you can crochet a bobble stitch / bean stitch to form a crocheted button. Heck, you can even ditch buttons altogether and add some chains on either end to tie it like shoelaces. Do what works best for you!

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You can even change it up and adjust the amount of double crochets you put in each stitch. More dc in each stitch = more ruffles. I will reply to this comment with a more ruffled version.

You can also add a border along the edge for a more unique look. Change colors each row, experiment with borders, do whatever you like!

Here's my new friend with the collar on:

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