The season centers on the friction and growing bond between the high-IQ world of science and the everyday life represented by Penny .
Rewatching today is a nostalgic trip. The iPhone had just been released in 2007; the characters don't have smartphones. They communicate via AOL Instant Messenger and landlines. A major plot point in Episode 7 involves a 300-page "Roommate Agreement" stored in a physical binder.
— Leonard and Sheldon clean Penny's apartment while she's asleep. The Fuzzy Boots Corollary