Umaro was originally supposed to be a random encounter on the world map and could only be caught with bait. Hidden game data suggests Umaro was at some point intended to be able to be encountered in the World of Balance, as an unused battle complete with stats and a simple AI script exists within the game's data.

According to Hironobu Sakaguchi, Umaro has a strong sense of honor and feels like he owes a debt to Mog, because Mog shared some food with him when he had collapsed from exhaustion.