Contextual graphics, part 3: frozen palette

When the end level sign lands in Lava Reef Zone 1, the palette animation on the foreground rocks suddenly freezes on whichever color it was at the time. Unlike previous cases however, this is not mandated by any particular line of code: it happens because the game silently transitions to act 2, which features no such animated palette!

It looks particularly dumb when it freezes on the bright purple color, which in turn is exacerbated by the fact that, at the start of the boss fight, the palette used by the foreground rocks is dimmed significantly. This was likely done in order to make the boss' giant hand stand out more as it emerges from the bottom of the screen.