Because level 6 is now a adventure level how about one of level being from Ape Escape? I even found some decent sprites for the monkeys.

gotten from here, http://www.freewebs.com/dark-blizzard/apeescape.png

What does Ape Escape have to do with adventure games?

Its a platformer and you explore different worlds/areas to catch monkeys.

If i recall Ape Escape is more of an ACTION game. But in world -1 it would maybe fit.