Position of glasses of milk in the beginning of the movie when Dennis is talking to his mother at breakfast.
In a scene Andy Milonakis' character Nick can be seen in the background of shot cleaning tables, without braids in his hair. In the next scene Nick has the braids in his hair and then decides to take them out.
When Justin Long makes his cameo, he says: "This is a bigger dump than the one I worked in." Problem is, this Shenaniganz IS the same one he worked at during the original movie. Evidence being that so many characters from the original movie still work there (or defected next door). It might be a different movie set, but it's not a different restaurant.
In one scene in the manager's office, you see Dan looking at the calendar, and he moves a post-it note for a tax audit to a different date. After that, throughout the movie, the date that the post-it note is on changes, and then towards the end of the movie, the post-it note is gone completely.