A controller is a console's most important "signature" outside of its game library. The SNES controller wasn't only more comfortable than the NES's boxy manner of input, it was also revolutionary: Even this current generation's controllers utilize button layouts that trace their origin back to Nintendo's classic A, B, X, Y setup.
You likely already know there are differences between the SNES controller and its Japanese Super Famicom counterpart. The Super Famicom's face buttons are merrily-colored (red, yellow, green and blue—like the Yoshis from Super Mario World!), whereas the SNES' face buttons are two different shades of purple. What you might not know is the controllers are otherwise universal. In fact, when you crack open an SNES controller, you can see embossed instructions on where to put each colored button—and the instructions cover both the North American and Japanese iterations of the controller.
"Lukerz03" posted a picture of their disassembled SNES controller on the Nintendo subreddit. You can clearly see where "Red, Blue, Green, Yellow" are etched on the inside of the controller's shell. Above that, we see "Purple" and "Lavender" for the North American assembly line. Yes, the inside of the controller shell is quite grimy. That just means the controller is well-loved. Let he who hath promised never to eat around their new game system a mere week before dropping a honey garlic drumstick on the controller cast the first stone.
There you go: A cool glimpse into the assembly of an SNES controller (with a bonus exhibition on what collects inside a controller after decades of use). Bonus fact: The SNES controllers' concave X and Y buttons are exclusive to the North American iteration of the system, and legendary game designer Shigeru Miyamoto was quite impressed with the addition. "By making [the buttons] concave, you can tell the difference between the primary and secondary buttons without looking at the controller," Miyamoto said in an interview published on Nintendo's site shortly before the launch of the SNES Classic. "That was impressive. I realized America has some outstanding industrial design."