Sir Weston and Boolossus were the hardest for me to get gold frames on. And yes, I did notice that the portraits change depending on the frame. I have all gold and an A ranking! Woooooooo!! (Then again, if I messed up on a portrait ghost or boss, I'd reset 'til I got it, which got very tiring after a while.)
Say...In the gallery those angel statues seem awfully suspicious to me... and those dirt-covered holes/pipes/whatever do too...
Oh, wait, when you said "Portrait Ghost" did you mean the battle against them or their picture? Fave battle was Melody Pianissima. (Gotta love that classic music.)
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If things don''t go your way, just keep complaining until your dreams come true.