Hallucination

A hallucination is a visual or auditory distortion that is mistaken for something real. These can be brought on by a variety of different factors, such as being under the influence of drugs.

Empath: The Luckiest Smurf stories
The Smurfs dealt with various types of hallucinations, either individually or as a group, in the EMPATH: The Luckiest Smurf story series. In the story "Days Of Auld Lang Smurf", the Auld Lang Syne Spell cast upon them caused most of them to experience the hallucination of their parents brought back to life, with Smurfette, Baby Smurf, the Smurflings, and Polaris Psyche being the only ones not affected by the spell.