Back in November I called your attention to a newly released complete version of the original Donkey Kong for the Nintendo Entertainment System. As you'll recall, the European exclusive included the cement/pie factory from the arcade game that did not make the jump to the home edition back in the 1980s. There was talk at the time that the new version of the game was actually a long lost prototype from the Nintendo vault, but now that the gaming community has had time to tear the new release apart and analyze it, there's speculation that it's not a prototype but a rather sloppy hack of the old home version. The Lost Levels forum has been doing some digging. Here's what forumite BMF54123 found:
Guys, I don't think this is a prototype at all, but an official Nintendo ROM hack.
The first half of the PRG ROM contains all the new data for the cement factory level, a copy of the title screen with the updated 2010 copyright, and a lot of code patches. The second half is identical to the US PRG1 ROM, except various routines have been hijacked to point to the new patches. A lot of them do really hackish things, like manually copying the entire sprite data page to unused RAM and shuffling it around (so the cement pies don't disappear), checking Mario's current animation frame to see if he's climbing (for the moving ladders?), and shoehorning in new data if the current level number is 02. It's also coded pretty sloppily in places, jumping to the same subroutine 5 times in a row, for example. This might explain why it glitches occasionally.
A true prototype would have certainly been built on the original source code, as Mario Bros. Classic was, not split into a bunch of patches. Whoever did this either didn't have access to the original source, or no longer had the necessary tools/knowledge to compile it.
So, is this new Donkey Kong a prototype or a hack? In the end it doesn't really matter, but it's one of those questions that tends to spark plenty of curiosity. There's pages of fascinating analysis at The Lost Levels that spins off into discussion about other instances of Nintendo hacking their own titles as the years go by when it comes to the Virtual Console and other such re-releases. It's not uncommon for the company to slightly improve their products over time through either returning to the original source code or just outright hacking, and this Donkey Kong discussion is the perfect excuse to explore a similar instance of revision.
Consider that aforementioned Classic Series version of Mario Bros., for instance, which was a 1993 European-exclusive NES release that boosted the older 1986 home version of Mario Bros. to closer approximate its 1983 arcade incarnation with the return of portions of the game that were originally removed due to cartridge space considerations and technical challenges such as extra frames of animation, the inclusion of different bonus stages, proper enemy introductions, and other fresh material thanks to advancements and improvements in the game development process of the era.
Reaching back further, that version of the game is based on a 1988 Famicom Disk System release called Return of Mario Bros. that was part of a promotion sponsored by Japanese company Nagatanien. This reworking of Mario Bros. included advertisements for Nagatanien's food products and current Nintendo releases as well as a contest opportunity in which codes generated by the game could be sent to the company for a chance to win Mario-related prizes and a copy of the latest major Mushroom Kingdom adventure, Super Mario Bros. 3.
Variants of Nintendo software have been around for ages. Some of them such as the new edition of Donkey Kong get a moment in the spotlight. Others like the many faces of Mario Bros. slip into obscurity. Sometimes what most players consider to be the only version of a game is actually the upgraded take on an original Japanese release (Zelda II: The Adventure of Link is a perfect example). Most go largely unnoticed due to the revisions occurring at the technical level as opposed to obvious cosmetic enhancements or gameplay alterations. Nintendo's revisionist history practices are nothing new and while they mostly may not matter to the average player, we can always count on dedicated fans with technical and historical expertise to alert the rest of us to interesting developments that may otherwise go unnoticed or overlooked. Sadly, sometimes this information comes with crushing disappointment. I hate to be the one to tell you this, but the deadline to enter to win Super Mario Bros. 3 from Nagatanien ended in May 1989.
Let us conclude with a look at the original box art for the Classic Series (or "Classic Serie" in its native language) edition of Mario Bros. It uses the early 1990s character models for Mario and Luigi and sports a familiar golden emblem that should be familiar to anyone who picked up the Wii release of Super Mario All-Stars in December 2010, providing yet another example of how Nintendo will gladly reuse and rework existing assets and material when it's appropriate to do so.