Movie that starts out like a wish.com The Hangover and ends with alien abduction

This is a weird movie I saw on Netflix about 15 years ago where a group of friends go to Vegas for a bachelor party, one of them joins a poker game against a group of people with maybe downs syndrome or some other learning disability, he loses and then on the drive home the movie COMPLETELY changes gears and they get abducted by aliens and it ends....darkly.