What happens when you keep people up for a long, long, long time? Lots. (Emphasis mine).

What they did
Notes and hallucinations

Bliss, Eugene L., Lincoln D. Clark, and Charles D. West. "Studies of deprivation sleep: relationship to schizophrenia." AMA Archives of Neurology & Psychiatry 81.3 (1959): 348-359.
Seven medical students were kept awake for 72 consecutive hours. Four subjects were given LSD-25 after 48 hours.
  • "[O]ne subject felt that the men's room seemed larger and the floor higher. The dark squares of the floor tile seemed to pulsate and would become darker, as well as larger, with every pulsation. A little later, he reported that the floor of the laboratory "seemed to be covered by a layer of shimmering water.""
  • Subject: "[A]s I walked down the hall, I thought I saw an old lady sticking her head out from the room. She seemed to have gray hair, which was rather 'frizzy.' I stopped to look again. She still had her head showing, and it did not move. It wasn't until about 10 yards from her that I realized it was a fire alarm box."
  • "One subject occasionally had the sensation of tunnel vision and another saw things shimmering and oscillating. He perceived the 'coke' machine and moving up and down."
  • Subject: "On one occasion I remember writing out a profound statement and ending the statement with the irrelevant comment 'owes $8.00.'"
  • "They forgot their fellow participants' names, and one had the nagging conviction that Ronald's (another subject) name was not Ronald but Robert."
  • "Time seemed to several to be a 'hodge-podge.' One felt the hours passed rapidly but that the days were interminable."
  • As part of the experiment, the subjects were asked to sit alone, facing a wall, with no conversation for five minutes, after which they recorded their thoughts. For the first two days , the recorded thoughts "related [to] jobs, girl friends, plans for parties, fishing, and the like." But by day three: "Fantasies frequently pertained to such topics as "cessation of the experiment and sleep" and "How much energy must be expended on keeping awake even for this five minutes of reverie?," "What do all these tests mean?," "Why doesn't Russia conquer Finland? ," "the cycles of sleepiness" and similar preoccupations.
Kollar, Edward J., et al. "Stress in subjects undergoing sleep deprivation." Psychosomatic Medicine 28.2 (1966): 101-113.
Four young-adult males were kept awake for 120 hours.
  • On the subjects: "Three of the 4 had full beards--and the fourth grew a beard a month later. Moreover, after the study began, 3 of the 4 had no compunctions about letting us know that they did not meet all of our criteria for selection."
  • "The beardless one, S 1, age 23, revealed that he was really an undergraduate and that he had no permanent residence but had been sleeping in his car for several weeks, using University facilities for study and for his toilet."
  • "S 4, age 30, a self-styled poet, was also married and and had not been enrolled as a student for several semesters. He was unemployed and had a 'pad' in a 'beatnik' section of Los Angeles."
  • "A group humor [developed]. Observers were in agreement that the subjects were entertaining and witty but many things which were hilarious for the subjects seemed meaningless to outsiders. The group resented any attempt by the staff to understand or to participate in the group jokes."
  • "Two walked into a wall because they had hallucinated an open door."
  • "All reported smoke and haze arising from objects. Two reported transient double vision."
Berger, Ralph J., and Ian Oswald. "Effects of sleep deprivation on behaviour, subsequent sleep, and dreaming." The British Journal of Psychiatry 108.455 (1962): 457-465.
Six male medical students (ages 21-24) were kept awake for four nights.
  • "All subjects experienced changes of visual perception of surfaces. Wallpaper patterns seemed to move and flow, swirling vapour or cobwebs or shimmering bubbles seemed often to cover the floor, their hands, or the table, and one man once spent half a minute carefully kicking at the cobwebs which appeared to cover a carpet. Two saw crumbs on the table-cloth running about like insects."
  • "Three had hallucinations of women peering at them... [For one subject], the women were almost all unpleasant old women, who appeared to be talking about him."
  • "...when asked to turn over all-night EEG recordings and write down the time every two minutes [they] often wrote down absurd phrases instead of the time (e.g., C.S. wrote, "Batting by one," "cormial brier," and "adorable.")"
  • "While C.S. was working through an EE record, he suddenly made the irrelevant remark, "Who to begin?" Soon afterwards, he kissed the EEG paper. When asked about this, he said he must have been dreaming about his girl friend (who was currently denying him her hand in marriage)."
  • "When asked on another occasion about a paint brush he was holding, he replied that the National Trust for Scotland were organizing an island visit."
  • "When J. D. said, "I can't find a towel", A.M. replied "Have you got diarrhoea?""
  • Subject describes the non-sequiturs in speech as his "own normal personality in conflict with another which seized upon some unrelated, irrelevant thought and gave voice to this thought in the middle of a conversation"
  • One subject becomes convinced that he has been given hallucinatory drugs and his experiences while under this misapprehension this are documented in detail.
  • Many other hallucinations not included here.
Luby, Elliot D., et al. "Biochemical, psychological, and behavioral responses to sleep deprivation." Annals of the New York Academy of Sciences 96.1 (1962): 71-79.
12 male subjects were kept awake for 123 hours.
  • "The visual phenomena were commonly described as fog, mist, or smoke issuing from under doors or from the walls. Geometric designs of great complexity were seen by an artist and confirmed in a kind of folie a deux by a younger subject whom he had treated paternalistically since the inception of the experiment."
  • "Although most subjects became paranoid, systematized delusions occurred in only one man. These developed at 100 hours and rapidly assumed very disturbing proportions. He had the conviction that his car had been stolen, that his fellow participants in the project were plotting to kill him, and that one attendant was going to stab him in the back with a pen knife. Strongly motivated by these fears, he attempted to protect himself by calling his wife to warn her that he might not survive, telling her to contact the "proper authorities." A strong belief in the reality of these experiences remained after 14 hours of sleep, although then his explanation was everyone acted that way because it was part of the experiment. One week later residues of paranoid thinking were still present."
  • "The paranoid delusional system developed by one subject in the group experiment can be interpreted by classical psychoanalytic constructs as a defense against homosexual impulses stimulated by interaction with the other men on the project."
Pasnau, Robert O., et al. "The psychological effects of 205 hours of sleep deprivation." Archives of general psychiatry 18.4 (1968): 496-505.
Four male subjects were kept awake for 205 hours.
  • "The subjects found the hours between 2 am and 6am extremely difficult. They devised the "basin of ice cubes face immersion" technique and found it to be the most successful method for fighting the waves of drowsiness."
  • "After the fourth day each subject expressed doubt and concern about the capability of the others to complete the experiment. Each denied self-doubts. They complained bitterly about the food, and focused much hostility on the medical student who drew the blood samples, referring to him as "Bela Lugosi.""
  • "Much time was spent decorating the ward with protest posters and a "thermometer chart" on which they marked off each successful hour."
  • "During the last three days of the deprivation, behavioral changes of a regressive nature were observed. Three of the subjects began "messing" in their food. Other infantilization of personal habits were noted including toilet and bathing activities. The subjects were intolerant of this behavior in the others while denying or ignoring the same activities in themselves."
  • "At 168 hours of sleeplessness, R.S. suddenly went "berserk" during the psychomotor tracking task. He screamed in terror and pulled his electrodes off and fell to the floor sobbing and muttering incoherently about a gorilla and repeatedly asking to be taken off the experiment."
  • Subject R.S. relates that "as he was tracking on the oscilloscope screen, it gradually changed and became Humpty Dumpty and the gorilla appeared in a corner of the room, then moved down and blended with Humpty Dumpty to form a composite figure which then moved menacingly toward him."
  • At the end of the experiment, all subjects are willing to remain awake for another day to reach the next payscale level ($400).
Katz, S. E., and Carney Landis. "Psychologic and physiologic phenomena during a prolonged vigil." Archives of Neurology & Psychiatry 34.2 (1935): 307-317.
A young man introduces himself to the experimenters and announces that he believes humans do not need to sleep. He volunteers to let them study him as he attempts to prove this. Ultimately, he goes without sleep for approximately 10 days, although he periodically dozes off during this time.
  • "He expected that at some time after a week of abstinence from sleep he would get a "second breath," and from that time on would be able to stay awake twenty-four hours a day without difficulty or effort. For several reasons we tried to discourage him..."
  • "His behavior and dress were somewhat eccentric. His age was 24 years."
  • "On one occasion when was asked what street corner he was on, he gave a location four blocks away from his actual situation. At another time he arose suddenly and walked to a desk which he mistook for a drinking fountain."
  • The subject reports hallucinations while crystal-gazing (done as part of an auditory test):

    "On the third day he saw a cottage by a beach, then other houses. He saw a man trying to burglarize one of the houses. The imagery was very vivid in the crystal.

    On the fourth day he saw a missionary in a roast pot with his knees hanging over the edge. The image turned into an old man in a bathtub with his knees hanging over. Then he saw a boy with cheeks puffed out giving a Bronx cheer. He had a hallucination that I tapped my hand between him and the crystal. He had visual hallucinations all day.

    On the fifth day he saw in the crystal a transatlantic whale with a square face. Then he saw very clearly two boats sailing across together. Most of the time he was in a daze and was hardly aware of my activity.

    On the sixth day he was unable to report a single image during the period of crystal-gazing.

    On the ninth day he was able to think only in fragments and had reminiscences. He saw several soap dishes, but he looked away most of the time.

    On the tenth day he was unable to report a single thought or image."
  • The subject writes a poem for two of them women who have been observing him during the experiment on the last day:

    "F unctions that hamper and gifts that requite
    M ust, by their nature in women unite.
    R eckless compounding of accent with flush
    A ttacks like a limen, basic in hush
    A ttacks in the crystal, survives in the light
    R ecoils and assembles 'twixt mystic and trite.
    N ew fashions go leering, old modesties blare
    I comin the springtime, their tortoise shell dare :
    O ver insistence, and collect what you may
    E voke pleasures of night to sustain in the day.
    N orthward the lust and the yearning conspire
    S weet south, how delightful sensed form to attire."