The Big Bang Theory: 10 Things You Completely Missed From Season One
5. Penny Can Sit On Sheldon's Spot
"That's my spot." Everyone who's had the misfortune of being acquainted with Sheldon has heard these chilling words any time someone sat on the left side of his couch. Because his seat is "in a state of eternal dibs", Sheldon will become flustered if anyone sits there. When he upset Howard, Sheldon allowed him to sit in The Spot to make amends but kicked him off after 94 seconds due to his attachment to his seat. Although most of Sheldon's quirks have been developed over time, The Spot has been canonised since the pilot.
But that doesn't mean he always abides by it. In the seventh episode, Penny was forced to stay at Leonard and Sheldon's place. When Leonard tells her to crash on the couch, Sheldon is instantly against it. At first, you'd assume he has taken umbrage at the idea of her resting on his Spot. However, he never mentions it.
In fact, he encourages her to sleep on The Spot so it will be easier for her to reach the door in case there's an earthquake. (This reasoning only makes sense in Sheldon's head.)