Well done. The force of clyde is strong in you. I've done my fair share of damage over the years (BB spindle, pedal spindles, etc.) but no crank arms that I remember. Impressive.
I suspect you're correct with attributing some portion of blame to the pedal extenders.
What make and model crank?
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Birth Certificate, Passport, Marriage License Driver's License and Residency Permit all say I'm a Fred. I guess there's no denying it.