There are 4 different versions of the Two Crude Dudes ROM that exist: NTSC (US), Japanese, PAL (EU) and NTSC-Prototype.

The Japanese version is called "Crude Buster" and the only differences between it and the NTSC version seems to be a different title screen logo, the 'alien' dogs are coloured like normal dogs, and the 'fake santas' are coloured red. The prototype version is simply the Japanese version halfway through being converted into the NTSC version and is basically the Japanese version but with the US title screen. The NTSC and Japanese versions are suitable for speedrunning, while the PAL version is significantly slower to run. The NTSC ROM is reccommended as there could be other differences in the Japanese version we don't know about.

The PAL version came out later and features many bug fixes and AI changes. One change that makes this version much slower for speedrunning is the lack of screen skipping. In the other versions, you can sometimes force the screen to transition where it would normally lock and require you to kill all the enemies. The exact mechanism for this is unknown but it generally happens when you play the game faster than it expects. This bug was fixed in the PAL version and can no longer be done.

Jumping is much slower on the PAL version and feels much "floatier". This slows down the run in various locations, such as the Power Cola bonus round.

Most bosses have had their AI tweaked in the PAL version, fixing many AI exploits that the current speedrun takes advantage of: • Heavy Snake - His jump now lands on top of you instead of just in front, meaning you can't sit in one spot and continually throw him. • Master Reaper - No noticeable changes. The exploit of sitting on the second step and kicking him repeatedly still works. • Rhino Man - He now jumps much further and cannot be immediately grabbed after he jumps/during his jump. Damage boosting through this fight still works. • Tiny Leo - Slight changes to how he attacks, the tactic of catching him as he jumps to the top level (see Murphagator's run) still works. The faster method of jump kicking also works but is significantly harder. • Nail Spider - Moves and attacks faster. The current method still works but is much harder. • Mad Scientist - Moves and attacks faster. Current method still mostly works but he will hit you each time.

And that's it! All the regional differences that I could find. If you'd like to speedrun this game the NTSC (recommended) and Japanese versions offer a lot more tricks and can be completed much faster.