Year 2018!

Since some of the characters are highly intelligent, maybe they could be fans not merely of comic book, movie, and TV science fiction but also of actual written science fiction.

And since the year is 2018, maybe one of the characters who has read James Blish's Cities In Flight series could comment about the difference between the real and fictional years.

For example, they could discuss the Star Trek episode "Space Seed" and someone could say something about no Eugenics Wars happening in the 1990s, and someone could say that space flight didn't become much faster around the year 2018 either. And someone could wonder why the Star Trek creators selected those dates. And someone could say that obviously they selected the 1990s to be before 2018, and selected 2018 as a homage to James Blish who wrote the written adaptations of the episodes.

And when the others wonder what that means, he could say that in Jame Blish's famous Cities in Flight series the novel They Shall Have Stars, also known as Year 2018!, was about the discovery of immortality drugs and faster than light space drive in 2018.

And someone could joke about how the fictional year 2018 was so much better than the real one.

But I don't suppose the creators of The Big Bang Theory know enough about written science fiction to write such a scene.