- "A happy way to die."
- ―Domino Walker on bad mushrooms[src]
Domino Walker was a dealer of hallucinogenic mushrooms and bounty head.
Walker grew his mushrooms on a ship. Among his buyers was Shaft and his older brother. After some time, he headed to Io. On the way, he had some problems with his ship, causing him to crash into the Bebop. Unwilling to stop, he kept going and landed on the moon. He proceeded to find more buyers for his mushrooms when he encountered Edward and Ein, who were looking for food. He also encountered Shaft again, who had tracked him down. He confronted Walker about the death of his brother after eating his mushrooms. Walker insisted it wasn't his fault for Shaft's brother's decision, but Shaft didn't accept it and chased him, shooting. Walker lost him and returned to his ship.
There, he gathered more mushrooms when he found Ed and Ein again, right there on his ship. Questioning who they were, Ed sprayed "stinky gas" at him, so he ran. Seeing Shaft again on the other side of a railroad crosswalk, he jumped onto the passing train to lose all three of his pursuers. However, Shaft was able to get on the train, as was Ed and Ein. Ein bit one of his bags, forcing Walker to drop it. The train soon halted due to a cow, throwing him and Ed to the ground. Walker convinced Ed that the bag of mushrooms was more valuable than his bounty, and escaped.