Famicom cartridges are much different from their American counterparts, but there was one particular difference that has been a mystery for years. Instead of indentations that were used to snap the cart in place, Famicom cartridges have holes. Surprisingly, this is something that Nintendo never explained, until now. In an interview with Japanese website Afternoon News, they revealed that the Famicom cartridges had holes on the top because “they were just part of the design”. Here’s the conversation they had about the cartridges in full:
Afternoon News: ‘I believe there are holes on the top of [Famicom] cartridges. Do you know what kind of meaning they had?’
Nintendo: ‘Yes, to be honest, they were just part of the design.’
Afternoon News: ‘Um, these aren’t holes made during the molding or the assembly?’
Nintendo: ‘That’s correct. They’re just [part of the cartridge’s] design.’
Afternoon News: ‘Then, the holes on the front and the back of Irem’s cartridges are also design?’
Nintendo: ‘That’s correct. Similarly, that’s the design.’

didn’t even know that would be a design until now.
That’s it?
It’s literally JUST for design?
What about those odd holes on the side of Konami Famicom games, such as King Kong 2? Those are the ones I always wondered about. If those are just for design, then it’s even more strange.
No it’s not! It’s more to it!….
Lol
not everything needs to have an explanation but i do feel like a cliff hanger on that answer.
||You silly humans, many things are off limits for your primitive brains, you can’t possibly understand our grand design…||
Not that it’s a big deal, but this answer has all the meat of a solid “Eh… because.” Lol.
Maybe the design is for air flow / heat dissipation?