In Episode 12 of the first season, after Shinku repelled Suigintou's fire attack back at her and her clothes burn off we see her torso is missing. after Shinku finish explaining how Suigintou was unfinished Suigintou's upper half falls to the ground.
Why it only when her clothes have been burned off does the reality of her floating upper half take effect? what was keeping both halves together as if she did have a torso?
There are quite a few differences between the anime and manga in Rozen Maiden.
Suigintou's torso is one of those.
In the anime, she has no torso connecting her upper and lower halves. Rozen Maker Wikia tells that it is shown in the two episedos of Rozen Maiden Ouvertüre that she was left incomplete and unassembled, not even receiving a Rosa Mystica. Her love for her father makes her able to move her upper body only. She is awarded a Rosa Mystica later.
There are no explanations to how she could move her both halves of her body without the connecting torso.
In the manga, Suigintou does have her torso. But she is ashamed of it, because it is defective, with cracks that cover most of her back, and through which her wings come out.
So the manga also does not offer an explanation, since the problem itself does not exist there.
