Howard and Sheldon feud over a parking spot.
Read MorePenny's Negative Externalities
A new part of the Roommate Agreement includes payments for all of Penny's bad habits.
Read MoreDinner Talk Externalities
Amy talks about tampons which upsets the guys.
Read MoreArguments as a Negative Externality
Leonard and Penny are in a huge fight.
Read MoreNeighbors as a Nuisance
When Sheldon learns that the neighbors above their apartment will move out, he begins to list all of the negative externalities that they didn't produce.
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