When Kelvin gives Rheya the pill to relax, note that she takes a sip of water first and then puts the pill in her mouth. When director, Steven Soderbergh, asked Natascha McElhone if she did this as a part of her performance, as possibly a statement that if "you are created by Solaris that is how you take a pill?" Natascha was confused and informed him that was simply how she took pills. See more...
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Continuity: After remembering the details of her suicide, Rheya is viewed from behind looking out the window and is sitting slightly to the right of the center of the window. In the next shot, when viewed from outside the window looking in, she is sitting to the far left of the (original) center. Even accounting for the change in camera angles it isn't even close.