Biggest "WHAT" in classic game buying?

[Tupin]

This page.

SNES isn't region locked, the cartridges are physically different, but the software is the same.

Isn't there an adapter to fit PAL and Famicom cartridges into an American SNES?

Several adapters, or you can get a clone system like Retro Duo to play it.

The problem with using a Game Genie as an adapter is that later SNES games refused to boot if they were booted with a Game Genie.

If you look inside an American SNES's cartridge port, you'll see two plastic blocks preventing you from putting a Super Famicom game in it. Some people open up their SNES's and remove these blocks, which will allow foreign games to work. Nintendo used the same method of regional lockout for the N64, which can be bypassed even easier. 

[jnfs2014]

Someone tried to sell a normal gameboy for $36.