The Werewolf Transformation - S5-E18
Continuity mistake: When Penny is giving Sheldon his haircut, she accidentally shaves the back of his head. The clippers are going from the bottom of Sheldon's hair, up to the top of his head. When Sheldon goes to leave the room, it can be seen only four or five inches from the back of his head have been shaved off.
The Werewolf Transformation - S5-E18
Character mistake: In S5-15, Sheldon is asking his friends to take him to SuperCuts. But in this episode, he goes to Mr. D'Onofrio's barber shop where he says he's gone to since he moved to CA, and he said D'Onofrio had his "haircut records."
Chosen answer: It does. The variable cleanliness of the cab and the habit of taxi drivers to engage customers in small talk would be too much for Sheldon to handle, and not an option for him.
Captain Defenestrator