I'm pretty sure the "Hangover" reference is to the series of (NSFW) still photos that played over the credits at the end of the first Hangover movie. Where they

I'm pretty sure the "Hangover" reference is to the series of (NSFW) still photos that played over the credits at the end of the first Hangover movie. Where they state "we're just going to look through these one time." https://www.youtube.com/watch?v=hBuwZEMMAOM https://www.youtube.com/watch?v=hBuwZEMMAOM (NSFW)