Quote Originally Posted by Squall of SeeD
It's never called "Earth" in Final Fantasy VII, though. As for the Supernova Spell, seeing as how it wasn't even really happening (the Spell can be cast several times, meaning those celestial bodies weren't being destroyed), and seeing as how a Spell capable of rendering that kind of destructive power would have rendered Meteor useless to begin with. With this in mind, I think the purpose of showing Pluto get shattered, Jupiter get a hole punched through it and then explode, and various other incidents of cosmic conflagration was to offer an emphasis concerning the Spell's strength by offering the destruction of worlds that the player would be familiar with. Which does beg the question of why the Spell isn't all that powerful.
I can't think of any other instance where a spell's visuals are used metaphorically, the things you described about the spell just enforce how immensely lame the spell actually is. Since at the climax of the spell the game clearly says "Earth" as a caption and shows your characters being scolded by the suns outer layer upon it, this spell DOES suggest that the planet is called Earth. There is no way around how uninspired and thoughtless the implementation of this spell into Safer Sephiroth's aresonal was.