In fact, "Are we there yet?" is so often said by children on road trips that it's become a joke. My kids will say it as we are leaving the driveway, just to be funny. Then they make the sound Donkey makes in Shrek on their journey to Far, Far Away. Then we tie them to the roof rack and continue in peace. Okay, not the last part.
There's a truly awful movie titled "Are We There Yet?" starring Ice Cube, about a man courting a single mother who agrees to take her kids on a road trip. I think they're making it into a T.V. series now, too. As Barb D notes, it is a very pervasive meme!