The Adventures of Bayou Billy is much harder than Mad City, the Japanese version of the game:

• Enemies in the beat-em-up stages move faster, deal twice as much damage, and take twice as many hits to kill.
• The optional alligator fights in the first few levels of Mad City are mandatory in Bayou Billy.
• The amount of ammo available at the beginning of the shooting stages is cut down from 150 to 50.
• There is less fuel for the car in the driving stages.

In the Japanese version of The Adventures of Bayou Billy, known as Mad City, there are four endings, with only the normal ending remaining in the international version of the game. The three additional endings are the following:

• If you grab any of the power-up bonuses you get from completing a Training stage (it doesn't matter which ones you get or whether you actually used them or not), the game will not show the ending upon beating it. A message will appear telling you to complete the game again without grabbing any power-ups and starts you back at the first stage.
• After beating the last boss, Annabelle will come out of a door and walk over to you. In Mad City, you can move around during this sequence, and if you avoid her for long enough, an ending will play where Annabelle concludes that Billy no longer wants her and leaves.
• If you let Annabelle hug Billy after she emerges, hold Up and Select together until the screen cuts to their faces. An alternate version of the normal ending will play where the dialogue will change to be written in Kansai dialect, and shows Billy forcing himself onto Annabelle.