I'm sure it started off small, like "Hey, we could throw a couch in the gym and watch a movie" and then grew to "Why not put a few couches in there" and somehow you end up with this:

A literal drive-in movie in the church gym. The kids seemed to have a lot of fun with it which is what really matters. The movie they watched was Extreme Days, a Christian made movie that's actually pretty funny and entertaining in spite of the predictable story and sappy romantic sub-plot. Worth a rental if you're just looking for a goofy movie.