In Advent Children (and Advent Children Complete, an extended version of the original), both Aerith and Zack make an appearance albeit posthumously. They both show themselves to Cloud in the form of spirits from the Lifestream, aiding Cloud in his battles by giving him guidance. They also appear in flashbacks from Cloud’s memory because the two figures’ fates become a catalyst in Cloud’s progressing depression, and are ultimately a key to the surrounding theme of Cloud overcoming his own guilt.

It should be noted that the two do not openly communicate in the movie, and only make their appearances in relation to understanding Cloud’s physical and emotional condition portrayed in the film. They do, however, share screen time at the end of the movie. After Cloud has finished cleaning himself of Geostigma, he sees the spirits of Zack and Aerith smiling at him as they turn to depart from the Church.