I had a copy of Lady Bug written by Arnim Laeuger, that I downloaded from fpgaarcade a long long time ago and forgot all about it. I recently came across it and I spent a little time getting it going for the Papilio. Unfortunately it won't fit on a Papilio One, it uses about 28 BRAMs and the Papilio One doesn't have any external memory and not enough internal memory.
Good news is, it will fit entirely into a Papilio Pro or any Spartan 6 FPGA without needing any external RAM or ROM. Getting this ported to the Papilio was just a matter of writing a top level module to connect the ladybug machine to the various ROMs and input controls. This is the first time I've finally used a PS2 keyboard controller from here which appears to have a well written bidirectional PS2 controller. Bidirectional means that when you hit for example the caps lock key, the PS2 controller detects that and sends data back to the keyboard to turn on the caps lock LED. The key mapping I chose can be easily changed if you look in the source code and have a handy PS2 key code reference. As is, the game should be playable with the arrow keys.
A small issue, if you have your monitor tilted one way to get other games like Pacman showing correctly, then Ladybug will appear upside down. If you can tilt the monitor the other way, you're all set, if however you can't and just reverse the state of the flip_screen_g variable, the screen will appear at first glance to be correctly flipped but unfortunately only the background is flipped, the sprites and key mapping are not, so, for example, Ladybug will appear to move the wrong way, won't line up with the corridors, eating the dots on one side of the screen causes the dots on the opposite side to disappear, etc.
Currently three games are supported: Ladybug, Dorodon (a Ladybug like clone) and Cosmic Avenger (a Defender like clone). I haven't searched what other ROMs the original hardware supported, if any.
The source code is available here. To make it all work, download the source then download and place the game ROMs into the appropriate ROMs folder. See the readme file in each folder for a list of the files and checksums you should be looking for, If you're on Windows, run the make_roms batch file in the relevant game rom folder. Game ROMs will be converted to vhdl files in the build directory. If you're on linux, there appears to be a makefile based system for creating ROMs and other files in the hex folder, seemed to work for me in MinGW, but I use Windows primarily. Once the ROM files are converted to VHDL, run the ladybug_papilio.xise project in the top directory and synthesize then upload to your board. You need a Papilio Pro with a Arcade Megawing and a PS2 keyboard in port "PS/2 B", VGA and audio connected. Enjoy!