They should have just made the first film and been done with it.
“The Hangover Part 3” drops the format of the previous two films and this time puts the three main characters, Phil played by Bradley Cooper, Stu, played by Ed Helms and Alan, played by Zach Galifianakis, into something entirely different. Gone is the plot of a bachelor party taken way too far. Instead, this time around the screen writers created an action-comedy it seems. Alan, who is for the most part a child in a man’s body, is off his medication and the rest of the cast, including the fourth character in the group who gets very little screen time, Doug, played by Justin Bartha, wants to take him to a rehab center.
As the four begin a road trip to take Alan to rehab, they come under attack from a newcomer to the series named Marshall, played by John Goodman, who knows about the group’s affiliation with the international criminal Mr. Chow, played by Ken Jeong. Because Chow stole from Marshall, Marshall takes Doug and says he will kill him unless Stu, Phil and Alan can capture Mr. Chow, setting up another trade-off scenario similar to the end of the first film.
Matthew Liedke on Film 