There's a request on mamecheat for Pocket Gal Deluxe, and I figured I'd give it a go. I played around for a bit, then discovered a nice, juicy string table with some intriguing bits of text. After a few hours of working backwards through the disassembly, I've discovered a number of interesting bits in the game!
Like other Data East games, hold P1 Start + P2 Start on game bootup to display the version.
Old/Unused Debug Menu Strings
Among the text in the string table were these lines of text, in successive order. They plainly appear to be lines from some sort of debug menu, to choose where to jump to. These lines are never actually referenced anywhere else in the code, making them completely unused. It may be from an older debug menu, or may just be the defaults from an SDK or 'example' program that was used as a base.
I've only included three screenshots of the text, since it's pretty bland. The full list in order is: WARNING, DECO MARK, OPENING DEMO, TITLE, IDLE, BEST PLAYERS, START DEMO
Winners Don't Copy
There's a security check at 0x0014CA that checks the values at four memory locations (0x0006E4, 0x0006EA, 0x0006EE, 0x0006F2) to make sure their values match against hard-coded values. If they don't, you'll be shown this snarky screen, obviously parodying the ugly FBI 'Winners Don't Do Drugs' screen of arcade games from the 90's.
This is the final text in the string table. It is unreferenced anywhere in the game, making it completely inaccessible normally. The last line is Japanese for 'Don't copy!'
It's interesting, because it's fully formatted to appear on screen, but the Don't Copy line makes me think it's only meant to be seen by someone poking around in the raw data (like a game pirate...)
Here's the big one. There is a fully functional debug menu left in the game. Game Mode brings you back to the game. Debug Mode is kind of a let down: it's simply a test of all the images in the game. There's a Sound Mode which is pretty self explanatory, and a Trick Mode, which lets you select the trick stages.
Here's the MAME cheat to access it (works for both European and Japanese versions):
<cheat desc="Debug menu"> <comment>Set this on the title screen then insert coins and hit start</comment> <script state="run"> <action>maincpu.pb@174101=80</action> </script> </cheat>
As simple as that cheat is, I spent several hours working backwards through the disassembly to find the proper way to access it. I actually haven't yet found out how it's normally triggered. There's only one place in the code where it is set, and that's during the Data East logo that appears only in the European version.