As for the header situation, here's what i discovered.



(before and after extraction, note that the ".nes" was added myself to make sure it could run on an emulator, as noted, the file was completely unnamed when i extracted it.)

and the result of doing a comparison after this?

Nintendo discovers iNES and, rather than sending a C&D, hunts down one of the devs and hires him to help implement a Game Boy emulator into Pokemon Stadium (Not to be confused with the US/EU release of the game, which is actually a sequel in Japan), released in 1998. Animal Crossing starts development on the Nintendo 64DD, at some point the decision was made to add playable NES games to it. So the team brought Tomohiro on board due to his experience with the hardware. With Tomohiro's help, the NES games are dumped internally for the game, most likely using the same tech the iNES team used, leading to the header issue. The fact that Clu Clu Land D lacks the standardized "FDS" header used by the emulation community at that point outright confirms they didn't "download the roms off the internet".

Bumping because i decided to do some research of my own (I'm working on a video series about the history of the three console manufacturers attempts at backwards compatibility/emulation re-releases over the years.)First off, calling Tomohiro Kawase the "Animal Crossing emulator" developer is a bit of an understatement. He (Alongside Hideaki Shimizu.) actually handled a lot of emulation projects for Nintendo. His first role at the company was making the "GB Tower" mode in Pokemon Stadium, which was effectively a Game Boy emulator that could run the 1st gen (2nd gen in Stadium 2/GS) mainline Pokemon games by inserting their carts into the transfer pak.In fact,Pretty much everything he's credited for involves it in some form, he's listed for "Connectivity Programming" in Metroid Prime (Which allowed you to play the NES Metroid on a Gamecube, unlocked by syncing a completed Metroid Fusion save file to the game using a link cable.) "engineering" on the Zelda Collector's Edition disc (Which was a compilation of NES and N64 games running on an emulator.) and even the "NES Emulator Programmer" on the(About 1:24 in if the timestamp doesn't work.)So it's highly likely he was indeed hired for working on iNES.The first thing i did was extract the Super Mario Bros ROM from Animal Crossing, a fairly easy task, as all the NES emulator content is conveniently stored in a single compressed file named "famicom.arc", which is then in turn stored as a bunch of ".szs" files. Using ARCtool and Uwizard in that order did the trick. Giving us a unnamed 41kb file.After verifying said unnamed file was indeed Super Mario Bros by using an NES emulator. I then acquired the Virtual Console version of Super Mario Bros. Thankfully, there's a tool known "vcromclaim" that completely automates the process of extracting VC titles, so i used that.This worked, but there's one problem. The file size is incorrect! Super Mario Bros is a 41kb game, while my dump turned it into. Fortunately, fixing it was pretty easy, it turns out VCromclaim grabbed a bunch of text and data from the VC emulator and appended it to the end of the rom. After chopping that out, the file size was fixed to the correct size of 41kb.Yep, the Virtual Console ROM does in fact originate from Animal Crossing. iNES header and all. In fact, all of the NES games in Animal Crossing have it, with the notable exception of Clu Clu Land D, which lacks a header entirely, starting with the "*NINTENDO-HVC*" text that is normally used by the FDS bios to verify that it's a legit disk image, the NES emulation community didn't start using standardized headers for FDS games until around November 1998 with the release of the fwnes emulator. About 3 months after the release of Pokemon Stadium, Tomohiro Kawase's first project at Nintendo.I feel like the most logical conclusion here is this.and that's basically everything you need to know about the subject.