Penny knocked on the door of Sheldon and Leonard's apartment. Leonard opened the door.
"Hello, Leonard. Hello, Sheldon. I have news for you."
"Is it anything we'd be interested in?" Sheldon inquired.
"What's up?" asked Leonard."
"I'm going to visit my cousins in Brooklyn, New York, for a couple of weeks."
"How fascinating," Sheldon said sarcastically.
"Yes, I'm really looking forward to it," Penny replied. "I've never been to Brooklyn before."
"And," said Sheldon, "I can assure you that you haven't missed a thing."
Leonard asked, "What do you plan to do in Brooklyn?"
"For one thing, I'm going to taste my very first egg cream."
"Oh, come on now," scoffed Sheldon.
"What do you mean, 'Oh, come on now'?" Penny demanded.
"I mean," Sheldon said, "that there is no such thing as an egg cream."
Leonard and Penny exchanged "is he serious? looks.
"Then why are there recipes for egg creams on the Internet?" Leonard challenged.
"And why," Penny added, "would my cousins have told me about egg creams if there is no such thing as an egg cream?"
"Penny," Sheldon said patronizingly, "let me ask you something. Were you ever taken to see Santa Claus when you were a child?"
"Of course. Why?"
"Well, as an adult, do you still believe that the man on whose lap you sat was actually," Sheldon made quotation marks with his fingers, "Santa Claus?"
"What is your point?" Penny asked.
"My point is that neither Santa Claus nor egg creams actually exist."
"This is a ridiculous discussion," Leonard said.
"I agree," said Penny.
"I can prove that the egg cream does not exist," Sheldon insisted.
"How?" Penny and Leonard asked in unison.
"What," Sheldon asked, "are the ingredients in a so-called egg cream?"
"Seltzer, chocolate syrup, and milk," Penny said.
"Exactly. Seltzer, chocolate syrup, and milk. No egg, and no cream. Ergo, no egg cream. I rest my case."
"Excuse me," Penny said, "I'll be right back."
She walked out the door.
Penny returned five minutes later with a glass in her hand.
"What," she asked, "do you see in this glass?"
"It looks like an egg cream," said Leonard. "Therefore," he turned to Sheldon, "I would have to say that Penny has presented conclusive proof that the egg cream does, in fact, exist."
"I shall prove otherwise," Sheldon responded. "Penny, please hand me that glass."
"All right," said Penny.
Sheldon drank the contents. He then went to the sink and rinsed the glass.
"You will notice," Sheldon said, "that this glass is empty. There is no egg cream in it."
"So?" Penny asked.
"So," Sheldon replied, with a mischievous grin, "I have demonstrated beyond the shadow of a doubt that the egg cream does not exist."