The joke was probably intended as a jab at unreasonable managers, but joke-Page did catch an important engineering flaw: After you use the wall-socket-powered time machine to travel through time, there is likely to not be a wall socket at your destination...

Depends on what principles the machine works. Realistically, it transfers information several milliseconds from future into present. Socket present.

Unrealistically, it can only travel couple of years into the future/past. Socket present.

Unbelievably realistically, it can travel hundreds or decades of years into the future/past. ???

Extremely realistically, it transfers information from the present to the future in realtime.

The joke is that it's a time machine. Someone brings a working one of those to office and I wouldn't care if it's powered by a butter churn.

You'll care if it's powered by something with a little more kick, like plutonium.

I think it being a time machine trumps its being powered by plutonium: go to future for cure to cancer, come back, and just like that, the plutonium is irrelevant.

the joke is why you're still depending on some manager's opinion, bringing it to his office (for what? for demo? for approval?) when you have invented time machine.

Just go back and in time and invent Google yourself, then you're the boss when you walk in with the time machine!