Answer: Hypnagogic hallucination
Explanation: The term 'hypnagogia' refers an individual's passage from being awake to falling asleep.
Hallucination refers to a virtual sensation, imagination, apparent feeling of a stimulus. Hallucinations are usually propagated on the mind of an individual without any real or actual occurrence of the imagined event. Hallucination affects one's senses as it seem to be very real, however, it isn't.
Hypnagogic Hallucination are therefore, apparent sensation or stimulus which are unreal propagated on the mind of an individual as the affected person transitions into sleep.