Sheldon: Oh, I see why you're confused. No, her news sounded important, but what your forgetting is it was an achievement in the field of biology. That's all about yucky, squishy things.
Penny: Honey, she's upset. You're her boyfriend. You have to at least try to be excited by the things she's excited by.
Sheldon: What if they simply don't excite me?
Penny: Well, just smile and think about koalas.