The cover of Charlie's book "The Attraction Equation" which is about an equation for friendship and attraction, is similar to the cover of John Green's "An Abundance of Katherines" which is about a teenager who tries to come up with an equation for relationships.
The Wexfords' front door is briefly visible at the start of the episode, and a Mezuzah is clearly visible on the doorframe. A Mezuzah is a small case containing a passage from the Torah (Deuteronomy 6:4-9), which Jews traditionally affix to the door frames of their houses as a constant reminder of God's presence; it also serves as a sign that the residents of that house are Jewish.