Harvey (Gabriel Macht) and Dana (Abigail Spencer) discuss drinking in the daytime. They joke saying, "They do it in Mad Men." Abigail Spencer was a cast character in Mad Men (2007).
In the scene where Louis is in Rachel's office, one can see an older couple behind him. That's Aaron Korsh's (creator of the show) parents, James and Nina Korsh. They are also the names of Mike Ross' parents.