Can you do any odd physical deformations/flexes?

[XR-7]

I also recall that when I've been sitting for a while (so usually in the mornings after waking up), I can twist my knees back and forth for infinite popping.  I can also bend both ankles upwards so that the tendon is on top of the bone instead of under, then flex them back down for lots of cracking.

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[randomtroll39]

I can crack my 2 pointer fingers

[Pie Crust]

I can make cracking sounds with my left arm. I just need a solid surface.