Penny grins and gives Sheldon her gift. "This is for you," she says, and when Sheldon is done unwrapping it she waits for an answer. Like a thank you Penny or a joyful exclamation or at least a kind word. Instead, since Sheldon is Sheldon and the rules of common mortals don't apply to him, Sheldon stares at the gift for a handful of seconds and then emits a noise that's halfway through a sniff and pure scorn. (By now, Penny is very good at identifying all the sounds Sheldon uses to express scorn. Sheldon manages to act scornful just by breathing.)
"Typical," Sheldon says. At this point Penny should give up and accept the fact that typical is all that Sheldon has to say about her present, but Penny just doesn't know how to give up. She's the queen of not giving up, as shown by her six years long acting career in which the highest point has been starring in an hemorrhoids commercial. Anyway, it took her time to choose a present for Sheldon, she purposefully picked something nerdy that he might like, she wants her thank you Penny.
"It's an Esperanto-Venusian/Venusian-Esperanto dictionary," Penny says, picking it up and waving it under Sheldon's nose. "Latest edition! Why don't you like it?"
Sheldon looks at her with pity. "Why don't I... Please," he says. "Never you mind, I don't want to hurt your feelings."
"No, come on, hurt them," Penny says. "If I didn't want to feel hurt on a daily basis, I don't think we could be friends."
Sheldon thinks about it. "Very well," he says. "First and foremost, I can't be friends with someone who can even just consider the idea of buying something like that."
Penny's smile freezes a little on her lips. "But... Esperanto-Venusian/Venusian-Esperanto!" she exclaims with a tinge of desperation in her voice.
"Penny, this isn't a serious dictionary, not at all," Sheldon says. "They're just made-up words! Venusian isn't even a language, they're not even saying which Venusians were talking about... Are they the Venusians from The Twilight Zone or those who made an appearance in Doctor Who? Of course, those are just the two most mainstream examples that come to one's mind, but they could also be the Venusians that Willy Wonka mentioned. It would be interesting to learn more, but without any additional information this book is an exercise in futility."
There's a pause while Penny tries to think. "But... latest edition!" she tries to say once more.
"To make an example that even you might understand," Sheldon says, "it's like writing a Human-Klingon/Klingon-Human dictionary. Which human language? Nobody knows! Do you think Klingons would buy such a dictionary?" he adds, giving her a look of pity.
Penny is very much tempted to throw her hands up in the air and leave slamming the door, but then she remembers that they're in her apartment and then she'd have to go to Leonard's, and it would be terrible to complain to Leonard only to find out that Leonard agrees with Sheldon on this subject.
So she makes a serious face and says, "Right, I'm so stupid, the made-up aliens would never buy that made-up dictionary."
The sarcasm goes all over Sheldon's head, because Penny is a great actress despite what several casting agencies might have told her in the past six years, and the book ends up balancing a rickety table.