Cat
Feline sleep disruption operates on a predictable schedule of maximum inconvenience. Cats demonstrate particular enthusiasm for activity between 3:00 and 5:00 AM, a window colloquially termed 'the zoomies' by exhausted humans attempting to impose scientific terminology upon domestic chaos.
Methods include but are not limited to: percussive investigation of closed doors, vocal performances at frequencies optimised for penetrating pillows, and the strategic deployment of body weight upon human bladders. The disruption proves difficult to prevent, as cats possess both the patience and the spite to outlast any defensive measure.
Fear
Fear-based sleep disruption lacks the cat's scheduling consistency but compensates through psychological depth. Anxiety attacks demonstrate particular affinity for the 2:00 to 4:00 AM window, manifesting as sudden wakefulness accompanied by conviction that all life decisions have been catastrophically wrong.
Unlike feline interruptions, fear-based awakening cannot be resolved through feeding or physical ejection from the bedroom. The intrusive thoughts simply persist, cycling through increasingly unlikely disaster scenarios until dawn renders them temporarily absurd. No amount of rational argument proves effective against 3:00 AM certainty that one has forgotten something essential.