[s2e17] The Terminator Decoupling -

Sheldon remains entirely indifferent to her celebrity, viewing her existence as a potential Skynet infiltration plot. 3. The "Penny-Sheldon" Remote Interaction

Sheldon insists on taking the train rather than flying.

In a highlight of the season, Penny loses patience with Sheldon’s complex instructions and simply smashes his puzzle box to get the drive. [S2E17] The Terminator Decoupling

Raj manages to talk to her after drinking what he thinks is beer, only to lose his "magic" when Howard reveals it is non-alcoholic.

While the boys are on the train, Sheldon realizes he left a flash drive with his research paper at the apartment. In a highlight of the season, Penny loses

Sheldon must guide Penny into his "sanctum sanctorum" (his bedroom) via phone.

Howard uses the pun "It's hot in here, must be Summer," which backfires so spectacularly that she eventually breaks his phone. Sheldon must guide Penny into his "sanctum sanctorum"

Sheldon simply loves trains, even if it means dragging the group through a 7-hour odyssey to meet Nobel laureate George Smoot. 2. The "Summer" Variable