Ending Your Movement

You can’t end your movement in the same square as another creature unless it is helpless.
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Very Small Creature

A Fine, Diminutive, or Tiny creature can move into or through an occupied square. The creature provokes attacks of opportunity when doing so.
Um, those two rules you quoted actually conflict one another on the very point Myou mentioned. I would argue that the Very Small Creature one is the "more specific" one (and therefore takes precedence) on the theory that most combat rules are written for the generic [medium] case and therefore that any rule specifically mentioning a size category is meant as an exception.