The Parking Spot Escalation - S6-E9
Corrected entry: For being smart they act stupid here. They don't think to alter the days the guys use the parking space with Friday being where they either share it together or Leonard or Raj get it while Howard and Sheldon would each get it two days apiece.
Correction: It's not a stupidity. It's entirely within the personalities of the two friends that Sheldon wouldn't accept change and give up something that is rightly his and for Howard to gloat over that he's a bigger deal than Sheldon now and refuse to give up something given for his new celebrity.
LorgSkyegon