Thus, there is no such thing as past lives according to Islam. Allah created us from nothing and gave us existence. We have only one life on this earth. After death we shall be raised up again on the Day of Judgment. There is no return to this life before the Day of Judgment.
People have all kind of imaginations.
Some time people imagine and dream things. That does not mean that this actually happened to them. Our mind works in so many different ways. The so-called recollections of lives before this life is nothing but hallucination.