It's the 1950s. Leo Fender had popularized the electric guitar, which of course, required an amplifier. Like his guitars, he picked the cheapest components, including knobs from old radios and a tweed covering meant for suitcases. 
Who knows what twist of fate turned a cheap-ass slab of basswood into one of the most expressive instruments invented in the 20th century. Or what turned a bunch of cheap off-the-shelf parts into guitar amps that would be revered and appreciate in price for 70+ years.
And what does this have to do with 3D printing? Looking at our collection of 3D printers, the thing that bugs me the most is the crappy knobs on the Prusa MK3. What better substitute than the same knob you'd find on a 1953 Fender guitar amp: the chicken head. To me, at least, it's cool as hell and the perfect combination of form and function. Last week, I had a rare free day, so I whipped up a chicken head knob facsimile that is a direct substitute for the Prusa knob.
Why bother with knobs? Who cares? When running a 3D print farm, one of the things I do all day is touch knobs. Knobs to run the Prusas, knobs to open and close the enclosure doors. Not to mention doorknobs, handles, and push plates. Anything you touch multiple times a day deserves to be looked at, optimized, and enhanced. Every single time I make a minor tweak to improve the product line, it helps in a field where we're just selling plastic boxes anyone can make.
I recently talked to an online marketing consultant who said all successful online companies don't give stuff away. To get the latest report from Formlabs, for example, you've got to give up your email and phone number so a salesperson can contact you later. He wants me to put the Prusa knob and other giveaways behind an email collection form. Screw that! One of the main perks of running a small company is treating customers how you'd want to be treated.
So download the STL or original design file (STEP format) for this Prusa knob with my compliments. Sign up for the newsletter or not: it's your choice. In the meantime, I'm field-testing more retro knob designs for our line of enclosures. Sign up for the newsletter and be the first to try them out :-)
I recommend printing this in ABS or PETG at .15mm layer thickness with a .4mm or finer nozzle. You won't need any supports. The rendering shows a traditional white stripe which you'd have to do with a brush and paint since most people don't have as an MMU2.
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