"Leonard, what does this mean?"
"It's a note, Sheldon, not a code. It means what it says: 'Sorry I finished your Wheaties. Penny.'"
"I can read. I was enquiring about the significance of the happy face. Was Penny smiling as she wrote this? Because if so, that seems particularly malicious. And even if she was smiling, I don't see how that information's pertinent to the primary message."
"It's not. It's additional social information."
"That Penny's happy she ate all the Wheaties? Wouldn't 'Mwahahaha' be more apropos?"
"Don't you think it speaks of a defective personality that someone would blatantly gloat—"
"—over the rampant disruption of a superior intellect's routine?"
"Sheldon. I'll go and buy you more Wheaties."
"Thank you, Leonard. And next time Penny stays over, tell her to bring her own cereal. Lol."