I doubt it's possible (don't quote me), but that'll take a huge chunk of file size anyway so there's no point. I'd suggest dividing the Big Shiee into a 3x5 space (a person is 1x1) and scale it to make it appear big. It's gonna look jagged, but so did many GBA and even DS games. Also Big Shiee only moves its cannons and track - the body doesn't animate (=change), so do some 1x1 partial sprites.