Sheldon: I was analyzing our lie and I believe we're in danger of Penny seeing through the ruse.
Leonard: How?
Sheldon: Simple: If she were to log on to SoCal physics group.org forward slash activities forward slash other, scroll down to seminars, download the PDF schedule, and look for the seminar on molecular positronium, well then, bippity boppity boo, our pants are metaphorically on fire!
Penny: Sheldon, have you any idea what time it is?
Sheldon Cooper: Of course I do. My watch is linked to the atomic clock in Boulder, Colorado. It's accurate to one-tenth of a second. But as I'm saying this, it occurs to me that you may have again been asking a rhetorical question.
Leonard: I already lied. Why cover it up with another lie?
Sheldon Cooper: Because your lie was painfully transparent, whereas my lie is exquisitely convoluted. While you were sleeping, I was busy weaving an un-unravelable web.
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