The entire night was caused because Alan (Zach Galifianakis) drugged the marshmallows.
Stu's (Ed Helms) future brother-in-law,Teddy, was stuck in the hotel elevator the whole time. He was safe and alive despite now missing a finger (We find out how he lost it during the photos in the credits).
Mr. Chow (Ken Jeong) was arrested in an international sting operation to catch him.
Stu stands up to his to-be father in law, and asks for his blessing. He receives it, and gets married.