Why does everyone always place Bilsy in Jungle? The location of JJ2 bosses always makes sense, if you ignore Bolly, who clearly should have been in Tubelectric, so there's no reason a demon would be the final boss of Jungle. I can think of three more likely options:

• Bilsy was the final boss of Medivo, until found to be overpowered. They removed him, but then Medivo was missing a boss, so they moved the closest one, because they couldn't allow that to happen in the final stage of an episode. This would explain the misplacement of Bolly, although Medivo, despite its somewhat hellish appearance, is also not the best placement for a demon boss.
• Bilsy was the final boss of Inferno. Inferno is the only world to have a boss in its first level, and there are also clear visual similarities between Bilsy and Bubba, meaning they were likely to exist in the same world. This hypothesis is supported by the fact Nick Stadler calls them collectively the 'boss characters in "Hell" levels' in his interview from 1997.
• Bilsy was a boss in the first level of Damn. This is not supported by any evidence, but it's clear he would fit into the theme, and as Damn is the final world, it wouldn't be unreasonable to think it might have had two bosses.