The sandwich Chuck is ordering in the shop from Lou (Rachel Bilson) is called a Rachel sandwich, which is a special version of a Reuben sandwich (substitution of corned beef with pastrami and coleslaw for sauerkraut).
In one of the scenes Chuck is making out in a car with Lou, while the car windows are covered in steam, and his hand is pressed to the glass. This is an allusion to the love scene in Titanic (1997).
Lou's Manager's "He had me at pastrami" quote is an allusion to the famous line said by Renee Zellweger, "You had me at hello," in the 1996 hit movie also starring Tom Cruise, Jerry Maguire (1996).