The Hangover Part II an exotic location. That's all I know". In January 2010, Phillips dismissed rumors that Zac Efron would join the cast of "The Hangover 2", though Ed Helms stated that Efron would be a welcomed addition, commenting, "I love that guy. He's actually really funny". In March 2010, Phillips denied reports that the film would take place in Mexico or Thailand stating, "I don't know. There's a lot of rumors. There was rumor also that it was going to Mexico or something and neither are true". Also by March, Galifianakis, Helms, Bradley Cooper, and Justin Bartha completed negotiations and signed deals
Hangover research of alcohol hangover is growing rapidly. The Alcohol Hangover Research Group had its inaugural meeting in June 2010 as part of the Research Society on Alcoholism (RSA) 33rd Annual Scientific Meeting in San Antonio, Texas. In 2012, Éduc'alcool, a Quebec-based non-profit organization that aims to educate the public on the responsible use of alcohol, published a report noting hangovers have long-lasting effects that inhibit the drinker's capabilities a full 24 hours after heavy drinking. In 2012, Las Vegas based Hangover Heaven, a mobile hangover treatment clinic, opened along with its Hangover Research Institute, which studies the treatment of hangovers.