When video game hunter Michael Leib ventured out to a garage sale at an apartment building up the street from his mother’s house in Burbank, he initially came across the typical things that you’d expect to see in a family-run sale: used kids clothing, ancient VHS tapes, well-loved stuffed animals.

Further digging into the piles of clutter uncovered some humdrum gaming-related items, like a non-working Xbox 360, a dusty Dreamcast, random Game Boy Advance titles.

Everything looked ordinary enough except for one Game Boy cartridge that caught his eye.

(Image source: Michael Leib)

The plain white label with the words “DMG-VUA Dr. Mario 1990 Nintendo Game Boy” didn’t look like any game that he had ever seen before. A single computer chip with a square quartz window protruded from an opening in the plastic case.

“Everything was cheap,” Leib said, “and I bought most of it except for the RROD 360.”

He added that the family aren’t to his knowledge “resellers,” meaning that he’s never seen them selling anything in the past whenever he’s driven by in the neighborhood.

“I have no idea how they got this [Dr. Mario cart]. It was totally out of place.”

Later Internet research revealed that he had picked up an actual first-party Game Boy prototype. He covered the exposed EPROM chip as a preventive measure against erasing the data, then placed Dr. Mario on eBay with a Buy-It-Now to test the auction waters.

That’s when your humble captain sailed in on the good ship Nintendo Player. After first sending in an offer of what I could reasonably afford at the time, my anxieties started working on me and irrational thought set in. Like a shotgun blast, I decided to end it all with a click.

Despite my now drained grocery account, I still had some Fruity Yummy Mummy cereal from Halloween to serve as my breakfast, lunch, and dinner for the next week until Thanksgiving. Then I could forage food from the relatives and hoard it away like a thieving little squirrel for the winter. (I’ll tell them I’m bringing along my friend Mario, and that he’s a really big eater, to make sure they stock up. What’s Thanksgiving with the family without a white lie or two?)

I blame the seductive label. I could not locate any other prototype examples that matched its distinctive design. European sample cartridges loaned to the gaming press come to close, but they’re far less sexy-looking without the gray lines underneath the text or the official Game Boy logo at the bottom.

You know you’ve got it bad when you forego grocery shopping over a fatal attraction to a Nintendo sticker. One day the next door neighbors will find my emaciated skeleton of a body sprawled out in a pool of the prettiest pieces of papered plastic they’ve ever laid their eyes on.

The “DMG-VUA” marking particularly piqued my interest, as this refers to Dr. Mario‘s Japanese cartridge ID. Although the Japanese and U.S. versions are identical, a Japanese region ID would suggest a greater possibility for potential differences, or earlier build leftovers, since the game was developed internally and released in Japan before anywhere else.

By comparison, shown above is a Super Nintendo sample of Super Mario All-Stars. Take note of the U.S. cartridge ID of SNS-4M on the front. Despite the American region code, cartridges like this have only been found overseas in countries like Sweden at Bergsala AB, Nintendo’s Swedish distribution center. They were reportedly sent to European game reviewers.

In addition to the Super Nintendo, other European samples for the original Nintendo Entertainment System and Game Boy have been found using the prefix cartridge IDs “NES-P” and “DMG-P,” respectively.

It’s been my experience that all three “SNS,” “NES-P,” and “DMG-P” types of cartridges contain nothing more than retail code.

This was not my first Dr. Mario Game Boy prototype. The previous one allegedly came from an internal development studio responsible for making official Nintendo strategy guides. Despite that promising provenance, the data ended up by matching the verified retail game, and has since been sold.

(Image source: Howard Phillips)

When former Nintendo of America Game Master and bow-tie aficionado Howard Phillips publicly resurfaced in 2012, he brought along with him a treasure trove of gaming keepsakes from his Howard & Nester days to share and to sell, including a loose “Virus” EPROM chip. The original name for Dr. Mario, Virus placed an emphasis on a sick bulldog being cared for by Nurse Toadstool. I reached out to Mr. Phillips about this mysterious chip to find out what system it belonged to, and he wrote back saying that he had tested the EPROM in an empty Game Boy development cart and the game would not run, leading him to believe that the item is instead one of the two chips from an old Nintendo Entertainment System build. That would explain the “2” handwriting, as the EPROM contains either CHR or PRG data.

That second chip may have been lost, but in early 2013, two other copies of Virus were fortunately located and uploaded online, along with an early Dr. Mario build. Before that, in October 2012, a PlayChoice-10 Virus prototype also found its way to the masses (link). Counting my now two Game Boy contributions, a grand total of six Dr. Mario prototypes have been backed up and shared publicly in the span of a little more than a year. An amazing feat, indeed, considering the elusiveness of Nintendo-produced development software.

So let’s start the operation on this second known Dr. Mario Game Boy prototype. Before anything else, the first thing I do with a prototype ROM image is run the data through a file comparison with a verified digital copy of the retail game. This time was no different, though I usually don’t do a double-take afterwards.

WindHex detected 1,495 different bytes. Dr. Mario is a 32KB game, so if my calculator is correct, those changes cover roughly 4.5% of the whole binary. To ensure the integrity of the prototype file, I extracted the cartridge’s data no less than four times using two different dumpers; all of the back-ups came out exactly the same.


Like Tetris, Dr. Mario is a simply made game, so I thought a basic playthrough might reveal some of the 4.5% that’s different. I thought wrong. After rediscovering just how much more difficult the Game Boy port is when compared to the Nintendo Entertainment System version, I could not spot anything altered in the menus, the gameplay, the Level 5/10/15/20 cutscenes, or the 2-player mode. Using the program GBgbs, I converted the prototype’s audio into a .gbs file, and couldn’t hear any changes in the music or in the sound effects, either.

The sprites appear to be the same, as well, except that they’re stored differently within the code.

Although there was no hidden text to speak of after converting everything to readable ASCII, the prototype’s internal header does spell the title as “Dr. MARIO” instead of being all in caps. That counts for something, right?

This puts me in a strange place. On the one hand, I’m elated to have redeemed myself from last time by actually acquiring a Dr. Mario that contains unique code. On the other hand, I can’t seem to locate anything noteworthy on or below the surface of the game.

The only thing to do now is release these monochromatic viruses to the world and hope that other gaming doctors out there put the prototype through their own X-ray machines to help find a cure to my raging ambivalence. If you need me, I’ll be chewing dry artificially-flavored mummy cereal as I wonder where my life went wrong.