Startling
Startling
[Cueball sits silently in front of his computer.] [Text block:] I still do this every few months.
[He continues to sit for two more panels.]
Cueball: Holy crap, it's the 21st century.

Cueball is startled every few months when he, again, realizes that he now lives in the 21 st century. When he grew up as a child, the year 2000 seemed very far away — it was the future, but he now exists in that timeframe with the rest of society.
The title text states that "the future" was reached in 2004... Three years before the comic was published. This is possibly a joke on how time works, as "the future" is always, was always, and will always be ahead of the time you're in. There may, however, be a reference to some movie set in the future year 2004....
The 21 st century, even the year 2004, was futuristic for people growing up in, for instance, the eighties. This view just belongs to the perspective of people — for people growing up in the '70s, the novel 1984 was even futuristic.
[Cueball sits silently in front of his computer.] [Text block:] I still do this every few months.
[He continues to sit for two more panels.]
Cueball: Holy crap, it's the 21st century.
