The plot of The Hangover centers around the enigma of what really happened the night before Phil (Bradley Cooper), Stu (Ed Helms) and Alan (Zach Galifianakis) wake up to a colossal mess in a hotel in Las Vegas, but what's the timeline of events on Doug's stag do? The mystery behind the monumental bachelor party - for the fourth friend who went missing - can actually be reconstructed.
The Hangover had an extremely positive reception among critics and fans, spawned two sequels, and became the highest grossing live-action comedy franchise of all time, despite being an original concept with no sci-fi or fantasy elements and a fairly untested set of leading actors at the time. It catapulted Cooper's career as an outright movie star and boosted the name of director Todd Phillips in Hollywood, allowing him to build the road to what would eventually be the highest grossing R-rated film ever with Joker, 10 years after The Hangover.
Most of the big surprises in The Hangover succeed at flipping the situation upside down because the trio runs into increasingly chaotic consequences of what they did the night before, like finding a random baby, an unknown tiger, and a naked Chinese man in the trunk of a car. Though the chase for Doug (Justin Bartha) requires the bulk of their attention, any hint at what they should expect next would have helped them understand where he is before the marriage ceremony begins. To their dismay, the consequences of their drunken adventure come faster than the exact memories of it. However, the end credits reveal photographic evidence of the team's repressed misadventure.
The Strip Club
The night starts out like rather tame in comparison to what comes next in The Hangover. The Wolfpack go to a strip club - a staple where stag parties are concerned. By this point, they already have more than replenished the alcohol levels in their systems despite multiple attempts by their bodies to expel the contents of their stomachs. Their ability to remember what they're about to do is long gone and way past the need for only one or two hangover antidotes.
Before arriving at the strip club, Stu steals the spotlight right away: he desperately chugs a whole bottle outside a liquor store, only to hurl it back out seconds later. This seems to make him even more stubborn on going all out. Indeed, he enacts his desires at their first stop. Phil and Alan get a private show from two of the strippers, but they seem turned off by the experience in comparison to Stu, who falls in love at first sight when he meets his soon-to-be-wife Jade (Heather Graham). His instant crush on the stripper is undeniable. He empties his wallet on her underwear while she performs for him and, as if that weren't enough, he is shown pulling his infamous tooth out with a heavy pair of pliers. He really seems to struggle with the incisor, as several different photos and expressions from his friends and Jade help corroborate.
The Chapel
Without a second thought, the whole Wolfpack is suited up with identical outfits at the chapel. Stu marries Jade and they all improvise wild poses for the photos, with Alan falling asleep on Stu's shoulder in one of them. They all seem a bit less intoxicated until they try to pose together with Jade. In the extended version of the slideshow, some of the pictures show a small brawl between Stu and Phil, apparently over touching Jade while holding her up in their arms.
Although Doug stared at her breasts first, Stu was distracted and continued to clown around. But out of the blue, Stu shoves Phil and then throws him on the ground, to which Alan responds with a punch. While all of this is going down, Doug's pants have gone missing - just like he will in a matter of hours. The next picture shows Stu almost kissing Alan, signaling their reconciliation. All of this materializes the charming chemistry that probably will remain untouched by a future Hangover sequel.
The Hospital
Only two photos that were taken at the hospital during The Hangover survive. One of them shows Phil lying on the bed with a bandage on his head and a bloodstain on his gown. Alan and Stu pose on either side, laughing at him. The absence of Doug may suggest he had already "disappeared", but Dr. Valsh (Matt Walsh) later reveals to the trio that he was actually there with them, therefore he was likely the one taking the pictures.
The second photo shows Phil immediately after, still drunk out of his mind, celebrating with half a bottle of alcohol in his hand. It turns out that his trip to the hospital was caused by a mild concussion and some bruised ribs, as Dr. Valsh points out. Dr. Valsh is the same doctor who let them know they had arrived at the hospital from the chapel, that Doug was still with them at that moment, and that they had Rohypnol - or roofies, administered by Alan - in their system the night before. When Phil later asked where the chapel was located, the doctor delivers one of The Hangover's funniest lines.
The Casino
To get to the casino, the squad had to first steal the police car in The Hangover. Otherwise, Dr. Valsh would have mentioned it when Phil insisted on trying to get more details out of him. Besides, Phil's stay in the hospital must have taken several hours, something which fits perfectly with the few photos that depict their crime with the vehicle. First, Alan is shown to be arresting a couple - who may or may not be in on it - with Phil laughing at them by his side, and Doug with a real rifle in his hands. This time, Stu is probably the one taking the pictures.
Before entering the premises, Alan shoots the rifle in front of the casino - which seemingly doesn't attract any attention, since their antics inside are very well documented. The gambling stint at the El Cortez casino marks the first chronological appearance of Mr. Chow (Ken Jeong), playing craps alongside an incredibly-focused Alan. The next picture contrasts this strange behavior with the sight of Alan passed out on the same table.
While Alan sleeps like a baby, the other three friends have a drink with famous Las Vegas singer and entertainer, Wayne Newton. Doug and Phil appear to be having a blast, but Stu doesn't hide his disdain for the singer. In the span of just a couple of photos, he has already picked a fight with him and his posse - and has surprisingly won with a left hook to the face.
Mike Tyson's House
As one of the most remembered elements of The Hangover franchise, Mike Tyson makes his debut due to the Wolfpack's drunken break-in in search of his tiger. In The Hangover, the heavyweight champion himself seeks out the trio and pressures them to return the wild animal after returning Doug's jacket, which he left in the tiger's cage that night. While watching the security footage of the crime at Tyson's house, they all notice how Alan peed in his pool and Phil made humping motions behind the tiger when they put it in the police car. The footage ends right after they're shown rolling on the floor in a fit of laughter while Alan vomits on the car's hood.
This is complemented with a few photos showing Doug riding the tiger like a horse and Alan playing with it like it was a little kitten. Also, they take a picture with the tiger inside the police car and a few others some minutes before, with the four of them posing alongside Tyson on his bed with a woman, deep asleep. Alan repeats his pattern from the past instances, falling asleep by his side.
Back at Caesar's Palace
Finally, after making a brief visit to Carrot Top and a tattoo parlor - where Alan gets his navel pierced - The Hangover's Wolfpack returns to the hotel. Alan receives oral favors from an older lady in an elevator and swims in the hotel's fountain. Then, the four friends dance for what appears to be several hours, befriend the female performers, warm up to Chow a lot further, and hump the chicken that will eventually walk around Stu's head in the opening scene. In the DVD commentary, director Todd Phillips clarified that they bought the chicken to feed Mike Tyson's tiger, which was already in the hotel room at that point since the valet later reveals to them that they came back with a police car instead of their Mercedes. Besides, the tiger couldn't have been partying with them at that moment.
All of this brings their adventure to the end of the night and the beginning of The Hangover. The final photos were taken on the rooftop, with Alan humping Doug on top of the mattress and sitting on him. Unknowingly to them, the craziest part of their trip was just about to start.