I'm guessing a photo of the drive-in screen would have turned out pretty trippy; sadly I didn't bring a camera. Here's an image I stole off the intertubes:

We have a three-screener here in Huckyland, and it's usually full on a weekend summer night. There's always a solid hour of waiting before the movie starts. Families spread out in folding chairs, bigger kids play catch, little kids already in their jammers and sleeping bags settle into the backs of pickups and station wagons and SUVs. When it begins to get dark people start honking their horns and flashing their headlights, not so much out of impatience as much as knowing that this is what they've done before every drive-in movie they've ever been to. It's ritual. And you don't f*ck with ritual.
No car-window speakers anymore - you tune into the movie with your radio (a different frequency for each screen). There are no ads before the movie. They show 3 or 4 previews and then the movie starts. There is an endless stream of people to the concession stand and the bathrooms, threading their way through multi-generation families eating twizzlers and melting ice cream cones and the worst popcorn ever made. Teenagers prowl the parking lots, hormones tap-dancing in their brainpans like popcorn. If you get bored with the movie you look at the sky; we were lucky enough this weekend to have a good thunderstorm in the distance to watch. If you get bored with the sky you watch the people. If you get bored with people watching, well, you're jaded beyond hope. Seek professional help.
The movie was Wall-e, a suprisingly good flick (you don't often see post-apocalyptic dystopia from Disney) until it remembers it's a Hollywood kid's movie and settles into requisite plucky-underdogs-band-together-and-save-the-day mode. Gotta send the kids home with a smile, right? I'm not complaining. I had a great time.
They even gave out free Wall-e watches, which hearkens back to my days of visiting the drive-in, when they always gave out free stuff. My favorite: a pouch of "green blood" given to everyone before showing the spectacularly weird "The Abominable Dr. Phibes." There's no mention of green blood in the movie. No matter.